Small Group Tutorials

Here to help students catch up, keep up, and move ahead. Book a consultation here.

Inequalities for Sengkang Families: Compare Values, Read Limits and Solve Clearly

Three secondary students learning together in a small-group tuition setting

eduKateSengkang · Family learning

Find your next learning step

Choose the question closest to yours. Read one useful section, try an example together, and return when you need the next step.

Route 1: Understand the signs — Read comparisons before manipulating symbols.

Route 2: Translate everyday limits — Separate below, at most and at least.

Route 3: Solve step by step — Keep the same set of permitted values.

Route 4: Practise and diagnose — Use worked answers to locate a specific misunderstanding.

Route 5: Support the next step — Find parent prompts and related reading.

Full chapter index · Subject learning hub · Sengkang neighbourhood guide

An inequality compares values rather than saying that they are equal. For Sengkang families helping with maths at home, the useful starting point is not a page of algebra. It is a sentence such as “we need at least six cards” or “the total must stay below twenty”. The mathematical sign records exactly which values are allowed.

Did you know? A single inequality can describe infinitely many answers. If a length is greater than three centimetres, four centimetres is possible, but so are three and a half and three hundred. If the unknown counts children, the possible answers change because a count must be a whole number. Meaning and arithmetic work together.

This guide builds from comparisons to simple linear inequalities through original family activities, worked examples and checks. The Sengkang settings are imagined learning situations, not venue rules, local prices or measurements. Choose one section for a short conversation at home, then carry the same question into a neighbourhood walk: what is fixed, what may vary, and is the boundary included?

Chapter index

Chapters 1–6: Start with a true comparison
  1. Start with a true comparison
  2. Make the symbol carry meaning
  3. Meet inclusive boundaries
  4. Use a number line without rushing
  5. Keep decimals and fractions in view
  6. Read negative comparisons correctly
Chapters 7–12: Translate at least and at most
  1. Translate at least and at most
  2. Distinguish below from no more than
  3. Define the unknown and its unit
  4. Separate equations from inequalities
  5. Test a proposed solution
  6. Use three boundary checks
Chapters 13–18: Add or subtract equally on both sides
  1. Add or subtract equally on both sides
  2. Multiply or divide by a positive number
  3. Why a negative multiplier reverses order
  4. Do not reverse for the wrong reason
  5. Solve a two-step inequality
  6. Simplify brackets carefully
Chapters 19–24: Unknowns on both sides
  1. Unknowns on both sides
  2. Recognise always true and never true results
  3. Combine two limits
  4. Model a budget without inventing prices
  5. Diagnostic: four short questions
  6. Diagnostic answers with reasons
Chapters 25–30: Practice: interpret boundaries
  1. Practice: interpret boundaries
  2. Practice: solve and check
  3. A paper activity for a neighbourhood day
  4. Turn a wrong answer into a useful explanation
  5. Parent questions that leave room to think
  6. FAQs and a sensible next step

CHAPTER 1 OF 30

1. Start with a true comparison

Back to contents

Place five counters beside eight counters. The first group has fewer counters, so write 5 < 8. Now read the statement aloud from left to right: five is less than eight. Reading matters because children sometimes recognise a familiar shape without knowing which quantity the sentence describes. Cover the symbol and ask for the words before asking the learner to write it.

The same relationship can be written 8 > 5, but the sentence now begins with eight. Neither group changed. Only the direction of reading changed. This is a helpful first distinction between changing a mathematical fact and expressing that fact another way. Invite your child to make both statements with the actual counters still visible.

Next compare five with five. Neither strict inequality is true; the appropriate relationship is equality. Finish with a small diagnostic: is 9 < 4 true, false or impossible to judge? It is false because nine is greater than four. A false statement is not meaningless. Recognising it gives a learner something precise to correct rather than a vague sense that symbols are difficult.

Contents · Next chapter

CHAPTER 2 OF 30

2. Make the symbol carry meaning

Back to contents

The open side of either strict comparison sign faces the larger value. That visual cue can help, but connect it immediately to words. With 12 > 7, the left quantity is larger. With 7 < 12, the right quantity is larger. Ask the child to point to the larger value first, then choose the sign and read the completed sentence.

A picture mnemonic is a temporary support, not the whole explanation. If the learner can draw a hungry animal but cannot explain 3 < x, return to comparisons using known values. Say, “Three is less than the number we have not chosen yet.” Try x = 6 and x = 1. One makes the statement true and the other does not.

Write several comparisons vertically instead of running them together: 14 > 10; 2 < 11; 6 = 6. This prevents a worksheet from becoming a visual guessing game. Once the child reads each reliably, ask for an example of their own and a deliberately false version. Explaining why the false version fails is often more revealing than completing ten nearly identical blanks.

Contents · Previous chapter · Next chapter

CHAPTER 3 OF 30

3. Meet inclusive boundaries

Back to contents

The signs ≤ and ≥ include equality. Read x ≤ 9 as “x is less than or equal to nine”. Nine itself is allowed. Read x ≥ 9 as “x is greater than or equal to nine”. Here nine is also allowed, but the permitted values lie on the other side. The short line under the comparison sign is doing important work.

Try four candidate values for x ≤ 9: 8, 9, 10 and 8.5. The first, second and fourth work if x may be any real number. Ten does not. If x counts whole cards, 8.5 would be excluded by the context, not by the inequality alone. Keep these two checks separate: does the value satisfy the comparison, and does it make sense as the quantity?

A good family prompt is “What happens at exactly nine?” This is a boundary question rather than a hint about an operation. It helps distinguish “no more than nine” from “fewer than nine”. Ask the learner to invent a sentence where nine is permitted and another where it is not. A strong explanation names both the direction and the boundary.

WordsComparisonBoundary allowed?
Fewer than sixx < 6No
At most sixx ≤ 6Yes
More than sixx > 6No
At least sixx ≥ 6Yes
Four common limit phrases, with x representing the stated quantity.

Contents · Previous chapter · Next chapter

CHAPTER 4 OF 30

4. Use a number line without rushing

Back to contents

A number line arranges values in order. Numbers farther right are greater; numbers farther left are smaller. Draw equally spaced marks for zero through ten, then ask where values less than four belong. Three is one example, but the region continues left. A number line is not just a list of possible answers; it shows their relationship.

For x < 4, mark an open circle at four and indicate the region to its left. The open circle says that the boundary itself is excluded. For x ≤ 4, use a filled circle at four. Explain the convention in words so a neat drawing does not hide an incorrect interpretation. The drawing and sentence should tell the same story.

Use a ruler or squared paper to keep spacing regular. Do not squeeze all the negative values into a tiny gap after deciding to add them later. If you cannot draw the entire infinite line, arrows indicate continuation. Ask your child to name one included value, one excluded value and the status of the boundary. Those three answers form a compact check of the whole representation.

Contents · Previous chapter · Next chapter

CHAPTER 5 OF 30

5. Keep decimals and fractions in view

Back to contents

An inequality such as x > 2 does not automatically mean x is at least three. That conclusion is true for an integer unknown, but not for a general number. Values such as 2.1, 2.01 and 2½ are all greater than two. Children who have mostly counted objects may need explicit experience of the spaces between whole-number marks.

Draw a short section from two to three and divide it into ten equal intervals. Put 2.4 at the fourth tenth after two. It belongs to x > 2 but not to x ≥ 2.5. Then place 2½ at the midpoint and connect it to 2.5. The inequality depends on value, not on whether that value is written as a decimal or a fraction.

Try this question: name a number between two and 2.1. One possible answer is 2.05. There is no single smallest real number greater than two. For any proposed answer above two, another can be found closer to two. You do not need to turn this into a formal proof; the practical lesson is to avoid silently treating every unknown as a count.

Contents · Previous chapter · Next chapter

CHAPTER 6 OF 30

6. Read negative comparisons correctly

Back to contents

On the negative side of a number line, −2 is greater than −7 because it lies farther right. The magnitude seven may look larger than two, but the negative sign changes the value. Ask the learner to locate both numbers rather than applying a rule about digits. A comparison concerns the whole signed number.

For x > −3, zero is permitted, but it is not the only possibility. So are −2, −1 and many fractions. For x < −3, values such as −4 and −10 work. Have the child test a value on each side of the boundary. This makes the direction visible and avoids the common claim that all negative numbers belong on the same side of every inequality.

If negative numbers are still unfamiliar, use the negative numbers family guide before adding algebraic transformations. A few minutes ordering signed values may repair an error that otherwise looks like an inequality problem. Return when the learner can explain why −6 < −1 without relying on the size of the unsigned digits.

Contents · Previous chapter · Next chapter

CHAPTER 7 OF 30

7. Translate at least and at most

Back to contents

Imagine a family making an original card game at a Sengkang kitchen table. A player needs at least six cards to begin. Let c be the number of cards. The condition is c ≥ 6, because six is enough and larger whole-number counts also qualify. “At least” names a lower limit, not an exact total.

Now change the rule: a hand may contain at most six cards. Write c ≤ 6. Six remains permitted, but seven is not. Ask for the smallest and largest values where the context supplies them. A hand cannot have a negative number of cards, so a fuller description is 0 ≤ c ≤ 6 with c a whole number.

Do not teach phrases as isolated code words without checking the sentence. “At least six cards are missing” describes a missing quantity, not the number still present. Underline the quantity represented by the letter before choosing a sign. A correct comparison attached to the wrong unknown is still the wrong model. The question “Six of what?” is small but remarkably useful.

Contents · Previous chapter · Next chapter

CHAPTER 8 OF 30

8. Distinguish below from no more than

Back to contents

Suppose an invented craft activity uses a ribbon shorter than twenty centimetres. If r is its length in centimetres, write r < 20. A ribbon exactly twenty centimetres long does not qualify. Change the instruction to “no more than twenty centimetres”, and r ≤ 20 is the right description. The boundary now qualifies.

Offer a counterexample to test each translation. If someone writes r < 20 for “no more than twenty”, try r = 20. The words permit it while the inequality rejects it, so the translation needs repair. This check is more dependable than asking whether the sign looks familiar. It compares the mathematical model with the original meaning.

In real life, measuring tools have limited precision. Keep that issue separate from the exact mathematical instruction used in the exercise. A ruler reading of twenty centimetres may be rounded; the idealised problem can still use an exact boundary. For an actual venue or activity rule, follow the current official instructions rather than treating an invented learning example as practical permission.

Contents · Previous chapter · Next chapter

CHAPTER 9 OF 30

9. Define the unknown and its unit

Back to contents

Before solving, write a short definition such as “t is the time in minutes” or “n is the number of notebooks”. This tells the reader what a candidate value means. If t = 12, that is twelve minutes, not twelve seconds or twelve people. Units should appear in the definition and in the final interpretation.

Consider “the walk takes less than half an hour”. If t is measured in minutes, t < 30. If h is measured in hours, h < 0.5. These expressions describe the same time limit in different units. Writing t < 0.5 while defining t in minutes would describe a completely different condition.

Use an imagined local outing rather than timing a child under pressure. Ask your learner to choose the unknown, state its unit and give an example of a permitted value. Then ask for one value that the statement rules out. If the child cannot explain their own letter, pause before doing algebra. A variable definition is not decorative working; it is the link between the symbols and the situation.

Contents · Previous chapter · Next chapter

CHAPTER 10 OF 30

10. Separate equations from inequalities

Back to contents

An equation asks for equality. An inequality asks which values meet a comparison. Compare x + 4 = 10 with x + 4 < 10. The equation gives x = 6. The inequality gives x < 6, which describes many possible values. Six is a boundary in the second problem, not an included solution.

A child may solve the equation correctly and then copy its answer into the inequality. Respond by substituting. If x = 6, the left side of the inequality becomes ten, and ten is not less than ten. If x = 5, the left side becomes nine, so the comparison is true. The arithmetic itself shows why one answer is insufficient.

Use the solving equations guide if balancing operations need attention. The useful bridge is that both topics involve preserving meaning while changing form. The important difference is the final object: sometimes one value, sometimes a whole region of values. Ask “What kind of answer is this question asking us to describe?” before writing the last line.

Contents · Previous chapter · Next chapter

CHAPTER 11 OF 30

11. Test a proposed solution

Back to contents

To test a value, replace the unknown everywhere it appears and evaluate the resulting comparison. For 2x + 1 ≤ 9, try x = 3. The left side becomes seven, and 7 ≤ 9 is true. Try x = 5, and the left side becomes eleven, which fails the condition.

Now test x = 4. The left side becomes nine, so the value works because equality is included. This boundary test is particularly helpful when the learner has chosen the correct direction but forgotten the line under the sign. Ask them to say the full comparison aloud, including “or equal to”, rather than glancing at it.

Testing a few examples can expose an incorrect answer, but it does not establish the complete solution set by itself. A child who checks three and four has not yet shown that all values at most four work. Explain the role of each method: substitution checks a candidate, while a justified sequence of algebraic steps describes every permitted value. Both are useful, but they answer different questions.

Contents · Previous chapter · Next chapter

CHAPTER 12 OF 30

12. Use three boundary checks

Back to contents

When a proposed answer is x ≤ 4, test a number below four, exactly four and a number above four in the original inequality. For 2x + 1 ≤ 9, x = 3 works, x = 4 works and x = 5 fails. These results match the proposed region. If they do not, inspect the algebra or the sign.

Choose nearby values because they reveal the boundary clearly. Huge numbers may confirm the direction but make the arithmetic unnecessarily distracting. If fractions are involved, pick simple ones. For x > ½, try zero, one half and one. Then add three quarters to remind the learner that the space between boundary and whole number contains valid solutions.

Teach this as a checking habit, not an extra ritual to perform mechanically on every easy comparison. The learner should understand why each test was chosen. Ask, “Which test tells us whether the boundary belongs?” and “Which tests tell us which side we want?” A short explanation gives you more information than a row of unexplained ticks.

Contents · Previous chapter · Next chapter

CHAPTER 13 OF 30

13. Add or subtract equally on both sides

Back to contents

Start with x + 5 < 12. Subtract five from both sides to obtain x < 7. The comparison direction stays the same. To see why, compare two known numbers: 3 < 8 remains true after subtracting five from each, giving −2 < 3. Equal shifts along the number line preserve their order.

Try x − 4 ≥ 9. Add four to both sides and obtain x ≥ 13. Test thirteen in the original statement: thirteen minus four is nine, so the inclusive boundary works. Test twelve and it fails. Say what the operation does rather than using “move the four across” as an unexplained shortcut.

A useful written layout puts one transformation on each line and aligns the comparison signs. This makes it easier to see whether the same operation was applied to the whole of each side. If the learner subtracts five only from the left, compare the new statement with the old one using a test value. The error is a changed relationship, not merely untidy presentation.

Contents · Previous chapter · Next chapter

CHAPTER 14 OF 30

14. Multiply or divide by a positive number

Back to contents

For 3x ≤ 18, divide both sides by positive three to get x ≤ 6. Positive scaling preserves order. Six is included, and five works as well. If x represents whole packs, the context may impose nonnegative integers; if x is a general number, the inequality itself allows negative values too.

Consider x/4 > 2. Multiplying both sides by four gives x > 8. Eight is not included because the original comparison was strict. Test x = 8: eight divided by four is two, not greater than two. A learner who changes > into ≥ during the calculation has changed the condition.

Before dividing, identify the sign of the divisor. It is not enough to see a multiplication and mechanically undo it. Positive and negative divisors affect comparison direction differently. At this stage, keep the multiplier explicitly known. Dividing by an unknown expression requires attention to whether it is positive, negative or zero, and belongs to a later discussion rather than an unannounced leap in difficulty.

Contents · Previous chapter · Next chapter

CHAPTER 15 OF 30

15. Why a negative multiplier reverses order

Back to contents

Begin with 2 < 5. Multiply both values by −1 and you obtain −2 and −5. On the number line, −2 is greater than −5, so the correct statement is −2 > −5. Multiplication by a negative number reverses their order. The sign change is a consequence of that reversal, not an arbitrary penalty attached to negative numbers.

Now solve −2x < 10. Dividing both sides by −2 gives x > −5. Check zero: the original left side is zero, which is less than ten, so zero must be included. Check −6: the original left side is twelve, which fails. These checks support the right-hand region rather than the left-hand region.

Use the wording “we divided both sides by a negative number, so the order reverses”. Avoid the broader but false statement “a negative sign means flip the inequality”. Adding a negative number does not reverse order. Subtracting a negative number does not reverse order either. The trigger is multiplication or division of both sides by a negative quantity.

Contents · Previous chapter · Next chapter

CHAPTER 16 OF 30

16. Do not reverse for the wrong reason

Back to contents

Solve x − 7 < 2. Adding seven to both sides gives x < 9, with no reversal. The expression contained a negative term, but the operation was addition. Now solve x + 3 > −4. Subtracting three gives x > −7. A negative answer does not require reversing the comparison.

Compare these with −3x ≥ 12. Here division by −3 gives x ≤ −4. Ask the learner to name the actual operation in each example before deciding what happens to the sign. This prevents a vague visual rule from spreading into every question that contains a minus symbol.

An error discussion can be brief and kind: “Your arithmetic found the right boundary. Let us check which side belongs.” Test one value on either side in the original inequality. The child sees that part of the work was successful while identifying the exact repair. There is no need to erase an entire solution or announce that the whole topic has been misunderstood.

Contents · Previous chapter · Next chapter

CHAPTER 17 OF 30

17. Solve a two-step inequality

Back to contents

Take 4x + 3 ≤ 19. First subtract three from both sides: 4x ≤ 16. Then divide by positive four: x ≤ 4. Keep the inclusive sign throughout. Explain the sequence in reverse-operation language: undo the added three before undoing the multiplication by four.

Now take 5 − 2x > 13. Subtract five to obtain −2x > 8. Divide by −2 and reverse the order: x < −4. Test −5 in the original expression: five minus twice negative five is fifteen, which is greater than thirteen. Test −4 and the two sides are equal, so it is excluded.

If the second example feels much harder, the obstacle may be signed arithmetic rather than inequalities. Work out 5 − 2(−5) separately, then return to the comparison. Keep explanations local to the error you see. A child who understands boundary inclusion but slips on multiplying two negative numbers needs a different next exercise from one who computes accurately and chooses the wrong solution region.

Contents · Previous chapter · Next chapter

CHAPTER 18 OF 30

18. Simplify brackets carefully

Back to contents

For 2(x + 3) < 16, one method is to divide by two first, giving x + 3 < 8, then subtract three to get x < 5. Another is to expand to 2x + 6 < 16 before continuing. Both preserve the same permitted values. Comparing methods can show that algebra is reasoning, not one fixed choreography.

Try −2(x − 1) ≥ 6. Divide both sides by −2, reversing the sign: x − 1 ≤ −3. Add one: x ≤ −2. Alternatively, expand to −2x + 2 ≥ 6 and solve. The final answer agrees. A frequent expansion error is to write −2x − 2 instead of −2x + 2.

Ask the child to choose the method they can explain most reliably. The shortest solution is not always the clearest at first. Once both approaches are secure, discuss efficiency. If an operation removes a bracket cleanly without creating extra terms, it may reduce opportunities for error. The checking method remains the same: substitute into the original statement, not only the simplified version.

Contents · Previous chapter · Next chapter

CHAPTER 19 OF 30

19. Unknowns on both sides

Back to contents

Solve 5x + 2 < 3x + 10. Subtract 3x from both sides to get 2x + 2 < 10. Subtract two, then divide by two. The result is x < 4. Subtracting the same variable expression is valid because it removes equal quantities from both sides for every fixed candidate value.

A second route subtracts 5x first: 2 < −2x + 10. Subtract ten to get −8 < −2x, then divide by −2 and reverse: 4 > x. This means the same as x < 4. Read the last line aloud before deciding that a different arrangement must be a different answer.

The first route avoids a negative coefficient, so it may feel easier. That is a strategic preference, not a requirement. Teach the learner to recognise equivalent comparisons in either order. A robust understanding survives a solution that ends with the boundary on the left. Ask for one candidate value to confirm that both final statements describe the same region.

Contents · Previous chapter · Next chapter

CHAPTER 20 OF 30

20. Recognise always true and never true results

Back to contents

Consider 2x + 3 < 2x + 7. Subtract 2x from both sides and obtain 3 < 7. This is true regardless of x, so every value in the stated domain satisfies the inequality. There is no single boundary to calculate. The unknown disappearing can be an informative result rather than a sign of failure.

Now consider 2x + 8 ≤ 2x + 5. Removing 2x gives 8 ≤ 5, which is false. No value of x can make the original statement true. Check any convenient value if the learner wants reassurance, but explain why cancellation settles every value at once: the same variable contribution appears on both sides.

Do not divide by zero to try to recover an unknown after the variable terms cancel. Read the remaining statement. If it is true, the entire allowed domain works; if it is false, none of it works. Context still matters. If x counts cards, “all allowed values” means whole nonnegative counts, not arbitrary negative lengths or fractional people.

Contents · Previous chapter · Next chapter

CHAPTER 21 OF 30

21. Combine two limits

Back to contents

An invented game asks a player to choose a whole number greater than two and no more than six. Write 2 < n ≤ 6. The allowed counts are three, four, five and six. The word “and” matters: a permitted value must satisfy both comparisons at the same time.

If n could be any real number, values such as 2.4 and 5.9 would also qualify. On a number line, show an open circle at two, a filled circle at six and the region between. Say explicitly that the two endpoint conventions are different. A child may know both symbols separately but still shade beyond a boundary when they first meet a combined statement.

Try translating the description before drawing it. Then test two, six and one number in the middle. This separates inclusion from direction. Do not read 2 < n ≤ 6 as a chain of arithmetic operations. It is a compact way of saying that n is greater than two and n is at most six. Expanding it into two sentences often makes the meaning immediately clearer.

Contents · Previous chapter · Next chapter

CHAPTER 22 OF 30

22. Model a budget without inventing prices

Back to contents

Use a made-up craft budget of twenty tokens. A starter set costs four tokens and each extra pack costs three. If p is the number of extra packs, the total is 4 + 3p. Staying within twenty tokens gives 4 + 3p ≤ 20, so 3p ≤ 16 and p ≤ 16/3.

The activity counts complete packs, so p is a nonnegative integer. The greatest permitted count is five, not 5⅓ packs and not six. Check the total for five packs: nineteen tokens. Six packs would cost twenty-two tokens, exceeding the limit. The algebraic bound and the contextual decision are different steps, and both should be shown.

This example is intentionally not a claim about any shop in Sengkang. Families can replace the tokens with their own invented numbers on paper. If using actual purchases, check current prices and the complete cost rather than relying on a teaching example. The transferable skill is to define the total, include fixed and variable parts, solve the comparison and return to what can actually be counted.

Contents · Previous chapter · Next chapter

CHAPTER 23 OF 30

23. Diagnostic: four short questions

Back to contents

Try these before reading the next chapter. First, write a comparison for “the number of cards is at least eight”. Second, decide whether 3.5 satisfies x > 3. Third, solve y + 6 ≤ 14. Fourth, solve −2z < 8. Ask for a sentence of explanation with each answer rather than only a symbol.

Let the learner choose the order. If the language question causes hesitation but the algebra is quick, focus on translating limits. If three and a half is rejected, revisit domains and number-line intervals. If only the last question goes wrong, inspect the negative-division step. The purpose is to locate the next useful lesson, not turn four questions into a ranking.

Keep the original working visible. A corrected answer without the original attempt can hide what changed. You might put a small note beside the error: “boundary included”, “fraction allowed” or “division by negative”. Those notes are more useful at the next practice session than a large cross. Stop after a clear explanation if attention is fading; a calm return later is entirely reasonable.

Contents · Previous chapter · Next chapter

CHAPTER 24 OF 30

24. Diagnostic answers with reasons

Back to contents

For the card count, c ≥ 8 is suitable once c has been defined. Eight is enough, and larger whole-number counts are permitted. For x > 3, the value 3.5 works because it is greater than three. The condition does not restrict x to whole numbers unless a context or instruction does so.

For y + 6 ≤ 14, subtract six from both sides to get y ≤ 8. Eight is included because 8 + 6 equals fourteen. For −2z < 8, divide by −2 and reverse the comparison to get z > −4. The boundary −4 gives equality in the original statement and is therefore excluded.

If the learner wrote z < −4, ask them to test zero. The original inequality becomes 0 < 8, so zero must be allowed. The proposed answer excludes it, revealing the directional error. Do not simply tell the child to memorise a flip. Use the comparison 1 < 3 and its negative multiples to rebuild the reason order reverses.

Contents · Previous chapter · Next chapter

CHAPTER 25 OF 30

25. Practice: interpret boundaries

Back to contents

Write each statement using a defined letter. A length is no more than twelve centimetres. A chosen number is below seven. A card count is at least four. A time is greater than five minutes but at most nine minutes. Decide whether the relevant boundary values are included before choosing a sign.

Answers are l ≤ 12 when l is length in centimetres; x < 7 for the chosen number; c ≥ 4 for the card count; and 5 < t ≤ 9 when t is time in minutes. Length and time also have physical restrictions, such as not being negative. Include those if the question asks for a complete contextual domain.

Extension: name a permitted value and a forbidden value for each statement. For the time interval, six minutes works, five does not and nine does. For the chosen number, 6.8 works unless the problem restricts choices to integers. This extension reveals whether the child is reading the meaning of the notation or merely matching a phrase to a remembered sign. Accept any correct examples with clear units and reasoning.

Contents · Previous chapter · Next chapter

CHAPTER 26 OF 30

26. Practice: solve and check

Back to contents

Solve these original inequalities: a + 7 > 12; 4b ≤ 28; 9 − 3c ≥ 0; and 2d + 5 < d + 11. Write one operation per line. For each final answer, choose one allowed value and verify it in the original inequality. Include the boundary in your checking conversation.

The solutions are a > 5, b ≤ 7, c ≤ 3 and d < 6. For the third, subtract nine to obtain −3c ≥ −9, then divide by −3 and reverse the sign. For the fourth, subtract d and then five. The resulting inequality is d < 6, not d = 6.

Useful checks include a = 6, b = 7, c = 2 and d = 5. The boundary values five and six are excluded in the first and fourth questions because the comparisons are strict. Seven and three are included in the second and third. If an answer is wrong, compare the first line that differs from the correct reasoning. Repair that decision before assigning a whole new set of questions.

Contents · Previous chapter · Next chapter

CHAPTER 27 OF 30

27. A paper activity for a neighbourhood day

Back to contents

Before an ordinary Sengkang outing, make six number cards: zero, two, three, four, six and eight. On paper, create three fictional sorting rules: less than four, at least four and greater than two but no more than six. Sort the cards under each rule separately. A card can qualify for different rules in different rounds.

For the first rule, zero, two and three qualify. For the second, four, six and eight qualify. For the third, three, four and six qualify. Ask why two is excluded from the last group while six is included. The contrast makes strict and inclusive boundaries concrete without requiring complicated arithmetic.

You can do the activity at home before leaving or while seated safely during a break. It does not require approaching roads, entering restricted spaces or treating public signs as a game. The educational connection to neighbourhood life is the habit of reading limits precisely. If a real sign gives instructions, follow it as written and check official guidance where needed; the homemade card rules do not replace actual conditions.

Contents · Previous chapter · Next chapter

CHAPTER 28 OF 30

28. Turn a wrong answer into a useful explanation

Back to contents

Suppose a learner writes x ≥ 5 for “more than five”. Ask, “Would exactly five be allowed by those words?” If they say no, point to the equality line in ≥ and let them repair it. The successful part is that they chose the correct direction; the repair concerns the boundary.

If a learner writes x > 4 after solving −x > 4, test five in the original expression. Negative five is not greater than four. Then test negative five as x: its opposite is five, which works. These two substitutions show why the solution must lie below negative four. The learner can connect the algebraic reversal to actual values.

Invite a short explanation in their own words: “I kept the boundary but selected the wrong side because I divided by a negative.” This is more informative than “I was careless”. Carelessness is a broad label with no clear next action. A specific explanation tells the learner what to inspect next time and lets the parent offer support without taking over the entire solution.

Contents · Previous chapter · Next chapter

CHAPTER 29 OF 30

29. Parent questions that leave room to think

Back to contents

Try “What does your letter represent?”, “Is the boundary included?” and “Can you name one value that works?” These prompts direct attention to structure without supplying the operation. If your child is stuck, choose one of them rather than delivering all three at once. Give a little quiet time for the answer.

When the arithmetic is correct but the interpretation is not, ask “Could that many complete packs exist?” or “What unit is this answer in?” Contextual questions encourage the learner to return to the original situation. When the sign is wrong, a boundary test or an easy substitution usually provides stronger evidence than repeated verbal correction.

Keep a session small enough to finish with a clear observation. For example: “Today you distinguished at least from more than and checked the boundary.” That is a concrete account of learning, not a promise about marks. If the child needs further instruction, bring one example with their reasoning to the teacher or tutor. A specific question about the exact step is easier to answer than a general statement that inequalities feel confusing.

A practical stopping check is to give a new example with the same structure but different numbers. After working on x + 5 ≤ 12, try x + 2 ≤ 10. Ask the child to describe what stays the same in the method and what changes in the boundary. This checks transfer without adding a more complicated operation. If the explanation remains clear, record the idea and leave the harder negative-coefficient example for another session.

Contents · Previous chapter · Next chapter

CHAPTER 30 OF 30

30. FAQs and a sensible next step

Back to contents

Does a strict inequality always have a greatest or smallest answer?

Not necessarily. For real x < 5 there is no greatest permitted value, because another can always be chosen closer to five from below. If x is an integer, the greatest permitted value is four. Domain information changes the answer.

Should children always draw a number line?

It is valuable when learning signs, boundaries or negative regions, but a confident learner may not need one for every simple algebraic exercise. Use it where it clarifies meaning. A drawing should support reasoning rather than become extra decoration that distracts from the original question.

What should we learn next?

Revisit equations and equal operations if transformations need support, or use the negative numbers guide if order and signs are the obstacle. For a family outing, keep the maths light: notice how words describe a limit, discuss one example and then enjoy the neighbourhood. Understanding grows through clear encounters, not through turning every moment into a test.

Can two inequalities look different and mean the same thing?

Yes: x < 7 and 7 > x describe the same condition. So do x + 2 < 9 and x < 7. The first pair changes the order of reading; the second uses an equal subtraction to simplify. Ask the learner to explain which kind of change occurred. This distinction helps them recognise a correct answer even when someone else writes it in a different form.

Contents · Previous chapter · Continue to the subject hub

Sources and further learning

OpenStax: further study of linear inequalities

Reviewed 21 October 2026. Examples, characters and practice data in this guide are original teaching material, not official school questions or observations of named families. Use the sections that fit the learner’s current understanding; this guide does not prescribe an age, school level or assessment result.