Primary 4 Math Sample Questions Explained
Singapore Math Drills Team · 22 September 2026
Primary 4 is often when maths questions begin to feel less like a list of calculations and more like a test of careful reading. Your child may know how to add, subtract, multiply and divide, yet still pause when a question asks what to do first. That is normal. A calm method helps them see the structure before choosing an operation.
This guide focuses on three useful Primary 4 skills: finding the perimeter of a rectangle, finding an unknown angle on a straight line, and finding the part of a quantity using a fraction. On the free sample worksheet, your child meets a short set of questions that practises these ideas with visual, step-by-step support. The examples below show how to talk through the thinking without taking over the problem.
Perimeter of a rectangle
A rectangle is 12 cm long and 5 cm wide. Find its perimeter.
Perimeter means the distance all the way around a shape. It is useful to imagine putting a ribbon around the outside of the rectangle. The ribbon touches every side, so we must include both long sides and both short sides. The diagram helps your child notice that the opposite sides of a rectangle have equal lengths.
- Walk around the four sides: 12 cm, 5 cm, 12 cm and 5 cm.
- Add them carefully: 12 + 5 + 12 + 5 = 34 cm.
- Use the rectangle shortcut as a second method: 2 × (12 + 5) = 2 × 17 = 34 cm.
- Check the unit. Perimeter measures length around the edge, so the answer is 34 cm, not square centimetres.
The long method is worth teaching first because it shows where the answer comes from. Once your child understands the four sides, the shortcut is efficient: add one length and one width, then double the result. Ask them to point to the two sides represented by each number before they calculate. This small habit links the picture to the arithmetic.
Common mistake: Multiplying 12 × 5 gives the area inside the rectangle, not the perimeter around it. Another common error is adding only 12 + 5, which counts just two sides.
Try this at home: Use a book or placemat, measure its length and width, and ask your child to find the distance around the edge in two ways.
Angles on a straight line
Find the unknown angle x. (48° given)
When two angles sit together on a straight line, they make a half-turn. A half-turn is 180°. This is the key fact, so encourage your child to say it before reaching for a calculator or writing an operation. The 48° angle and the unknown angle are not equal angles; they are the two parts of one straight angle.
- Identify the whole: the straight line represents 180°.
- Identify the known part: one angle is 48°.
- Subtract the known angle from the whole: 180° − 48° = 132°.
- Check by adding the two parts back together: 48° + 132° = 180°.
The check is especially helpful when the unknown angle looks obtuse in the visual. A result of 132° is bigger than 90° but smaller than 180°, so it fits the picture. Your child does not need to memorise a new rule for every drawing. They can ask, “What whole angle do these two parts make?” and then use subtraction.
Try turning the page or drawing the same idea in a different direction. The line can be horizontal, vertical or slanted; its orientation does not change the fact that a straight-line total is 180°. This is a good way to separate the mathematical relationship from the appearance of the diagram.
Common mistake: Some children use 90° because they see two angles next to each other, or 360° because they remember a full turn. Ask whether the arms make a half-turn or a full turn before choosing the total.
Try this at home: Draw a line, mark one angle with a protractor or a careful estimate, and ask your child to find the angle next to it and explain why the pair totals 180°.
Fraction of a quantity
Priya had $96. She spent 3/8 of it. How much money did she have left?
This is a fraction question with two parts: the amount spent and the amount left. The question asks for the amount left, so finding 3/8 of $96 is only a middle step. A units table or part-whole bar makes that distinction visible. The whole $96 is split into 8 equal units, and the spent portion takes 3 of them.
- Read the denominator first. The 8 means the whole amount is divided into 8 equal units.
- Record the whole: 8 units = $96.
- Find one unit: $96 ÷ 8 = $12.
- Find the amount spent: 3 × $12 = $36.
- Find the units left: 8 − 3 = 5 units.
- Find the money left: 5 × $12 = $60.
- Check the whole: $36 + $60 = $96.
| Part | Units | Amount |
|---|---|---|
| Spent | 3 units | $36 |
| Left | 5 units | $60 |
| Total | 8 units | $96 |
The shortcut gives the same result. If 3/8 was spent, then 8/8 − 3/8 = 5/8 was left. Therefore, 5/8 × $96 = 5 × ($96 ÷ 8) = 5 × $12 = $60. The units method is often easier to explain because every number has a picture: eight equal parts, three used, five remaining.
When your child reads a fraction word problem, encourage them to circle the words “spent”, “left”, “more” or “remaining”. These words identify which part the question wants. They can also draw a quick bar with eight equal sections and label three as spent. It is much harder to accidentally stop at $36 when the bar clearly shows that five sections are still unaccounted for.
Common mistake: Giving $36, the amount spent, instead of $60, the amount left. The fraction calculation is not finished until the wording of the question has been answered.
Try this at home: Give your child a pretend budget of $40 and ask them to spend 3/8, then explain how many equal units remain and how much money that represents.
How Singapore Math Drills helps
The free sample mini-drill gives your child a small, manageable place to practise these kinds of questions. The question bank includes heuristics and PSLE-style word problems, while progressive hints and worked solutions reveal the next idea only when it is needed. Adaptive practice can then adjust future practice to the skills your child is still building, and spaced review brings older skills back before they fade. For questions that need a drawing or a bar model, the built-in scratch pad gives your child a place to show the working beside the problem. The aim is steady understanding, not rushing through a long list.
Try one yourself
Wei Ming had 140 cards. He gave away 2/7 of them. How many cards did he have left?
Hint: 7 units = 140, so 1 unit = 20. He kept 5 units.
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