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Primary 6 PSLE Mathematics Problem Solving Heuristics Quiz

Free P6 PSLE Maths Problem Solving Heuristics quiz, Exam version, with questions, answers, and PSLE-focused practice for Singapore students.

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Primary 6 PSLE Mathematics From Real Exams Generated by DeepSeek V4 Flash Sample 01 Updated 2026-08-17

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Answers

Answer Key: Primary 6 PSLE Mathematics Quiz - Problem Solving Heuristics

Total Marks: 50


Section A: Short Answer Questions (Questions 1 to 5)

Each question carries 2 marks.

1.

  • Answer: 15 eggs
  • Working:
    • 3 eggs → 8 cupcakes
    • 1 cupcake → 3/8 eggs
    • 40 cupcakes → 40 × 3/8 = 15 eggs
  • Marking Notes: 1 mark for correct method, 1 mark for correct answer.
  • Common Mistake: Students may incorrectly multiply 3 × 5 = 15, but the correct reasoning is unitary method.

2.

  • Answer: $12.50
  • Working:
    • 3 pens → $2.50
    • 1 pen → 2.50÷3=2.50 ÷ 3 = 0.8333...
    • 15 pens → 15 × 0.8333...=0.8333... = 12.50
  • Marking Notes: 1 mark for correct method, 1 mark for correct answer.
  • Common Mistake: Students may incorrectly calculate 15 ÷ 3 = 5, then 5 × 2.50=2.50 = 12.50. This is also correct.

3.

  • Answer: 300 km
  • Working:
    • Speed = 120 km ÷ 2 h = 60 km/h
    • Distance = 60 km/h × 5 h = 300 km
  • Marking Notes: 1 mark for correct method, 1 mark for correct answer.
  • Teaching Note: This is a direct application of the formula: Distance = Speed × Time.

4.

  • Answer: 360 g
  • Working:
    • 6 people → 240 g
    • 1 person → 240 g ÷ 6 = 40 g
    • 9 people → 9 × 40 g = 360 g
  • Marking Notes: 1 mark for correct method, 1 mark for correct answer.
  • Common Mistake: Students may incorrectly add 240 + 120 = 360 g, but the unitary method is more reliable.

5.

  • Answer: 120 toys
  • Working:
    • 3 hours → 45 toys
    • 1 hour → 45 ÷ 3 = 15 toys
    • 8 hours → 8 × 15 = 120 toys
  • Marking Notes: 1 mark for correct method, 1 mark for correct answer.
  • Teaching Note: This is a rate problem. The rate is 15 toys per hour.

Section B: Structured Questions (Questions 6 to 10)

Each question carries 3 marks.

6.

  • Answer: 58 flowers
  • Working:
    • First 5 rows: 5 × 8 = 40 flowers
    • Next 3 rows: 3 × 6 = 18 flowers
    • Total: 40 + 18 = 58 flowers
  • Marking Notes: 1 mark for each correct step, 1 mark for final answer.
  • Teaching Note: This is a multi-step problem. Break it down into parts.

7.

  • Answer: 8 chocolates
  • Working:
    • Total: 24 chocolates
    • Jane takes: 1/3 × 24 = 8 chocolates
    • Remaining: 24 - 8 = 16 chocolates
    • Brother takes: 1/2 × 16 = 8 chocolates
    • Left: 16 - 8 = 8 chocolates
  • Marking Notes: 1 mark for each correct step, 1 mark for final answer.
  • Common Mistake: Students may incorrectly calculate 1/2 of 24 = 12, forgetting that the brother takes half of the remaining chocolates.

8.

  • Answer: $45
  • Working:
    • Number of bags: 120 ÷ 8 = 15 bags
    • Total money: 15 × 3=3 = 45
  • Marking Notes: 1 mark for correct number of bags, 1 mark for correct total, 1 mark for final answer.
  • Teaching Note: This is a two-step problem. First find the number of bags, then the total money.

9.

  • Answer: 15 minutes
  • Working:
    • Combined rate: 5 + 3 = 8 litres per minute
    • Time = 120 litres ÷ 8 litres/min = 15 minutes
  • Marking Notes: 1 mark for combined rate, 1 mark for correct method, 1 mark for final answer.
  • Teaching Note: When two taps work together, their rates add up.

10.

  • Answer: $390
  • Working:
    • Bus cost: $240
    • Entrance fee: 30 × 5=5 = 150
    • Total: 240+240 + 150 = $390
  • Marking Notes: 1 mark for entrance fee, 1 mark for correct total, 1 mark for final answer.
  • Common Mistake: Students may forget to include the bus cost.

Section C: Problem-Solving Questions (Questions 11 to 15)

Each question carries 4 marks.

11.

  • Answer: $39.60
  • Working:
    • Original price: $45
    • 20% reduction: 20% of 45=45 = 9
    • Sale price: 4545 - 9 = $36
    • 10% increase on sale price: 10% of 36=36 = 3.60
    • Final price: 36+36 + 3.60 = $39.60
  • Marking Notes: 1 mark for each correct step, 1 mark for final answer.
  • Teaching Note: The percentage increase is applied to the sale price, not the original price. This is a common error point.

12.

  • Answer: 36 m²
  • Working:
    • Outer area: 12 m × 8 m = 96 m²
    • Inner dimensions: length = 12 - 2 = 10 m, width = 8 - 2 = 6 m
    • Inner area: 10 m × 6 m = 60 m²
    • Area of path: 96 - 60 = 36 m²
  • Marking Notes: 1 mark for outer area, 1 mark for inner dimensions, 1 mark for inner area, 1 mark for final answer.
  • Common Mistake: Students may subtract only 1 m from each side instead of 2 m (1 m on each side).

13.

  • Answer: 72 red marbles
  • Working:
    • Red : Blue = 3 : 2 = 6 : 4
    • Blue : Green = 4 : 5
    • Red : Blue : Green = 6 : 4 : 5
    • Green = 60 marbles → 5 units = 60 → 1 unit = 12
    • Red = 6 units = 6 × 12 = 72 marbles
  • Marking Notes: 1 mark for finding common ratio, 1 mark for finding value of 1 unit, 1 mark for correct answer, 1 mark for clear working.
  • Teaching Note: To combine ratios, make the common term (blue) the same in both ratios.

14.

  • Answer: 120 km
  • Working:
    • Let distance = d km
    • Time from A to B: d/60 hours
    • Time from B to A: d/40 hours
    • Total time: d/60 + d/40 = 5
    • Common denominator: (2d + 3d)/120 = 5
    • 5d/120 = 5
    • 5d = 600
    • d = 120 km
  • Marking Notes: 1 mark for setting up equation, 1 mark for correct algebra, 1 mark for correct answer, 1 mark for clear working.
  • Teaching Note: Use the formula Time = Distance ÷ Speed. The total time is the sum of the two times.

15.

  • Answer: 12 friends
  • Working:
    • Let original number of friends = n
    • Let original cost per person = $c
    • Total cost = n × c
    • With 4 more friends: (n + 4)(c - 6) = n × c
    • With 3 fewer friends: (n - 3)(c + 8) = n × c
    • From first equation: nc - 6n + 4c - 24 = nc → 4c - 6n = 24 → 2c - 3n = 12
    • From second equation: nc + 8n - 3c - 24 = nc → 8n - 3c = 24
    • Solve simultaneously:
      • 2c - 3n = 12 → 2c = 12 + 3n → c = 6 + 1.5n
      • Substitute: 8n - 3(6 + 1.5n) = 24
      • 8n - 18 - 4.5n = 24
      • 3.5n = 42
      • n = 12
    • Original number of friends = 12
  • Marking Notes: 1 mark for setting up equations, 1 mark for correct algebra, 1 mark for correct answer, 1 mark for clear working.
  • Teaching Note: This is a challenging problem that requires setting up two equations and solving them simultaneously.

Section D: Challenging Problem-Solving Questions (Questions 16 to 20)

Each question carries 5 marks.

16.

  • Answer: $5 profit
  • Working:
    • Total cost: 200 × 0.50=0.50 = 100
    • 60% of 200 = 120 eggs sold at 20% profit
    • Selling price per egg (profit): 0.50×1.20=0.50 × 1.20 = 0.60
    • Revenue from 120 eggs: 120 × 0.60=0.60 = 72
    • Remaining: 200 - 120 = 80 eggs sold at 10% loss
    • Selling price per egg (loss): 0.50×0.90=0.50 × 0.90 = 0.45
    • Revenue from 80 eggs: 80 × 0.45=0.45 = 36
    • Total revenue: 72+72 + 36 = $108
    • Profit: 108108 - 100 = $8
  • Marking Notes: 1 mark for total cost, 1 mark for revenue from profit eggs, 1 mark for revenue from loss eggs, 1 mark for total revenue, 1 mark for final answer.
  • Teaching Note: Profit percentage is calculated on the cost price. A 20% profit means selling price = 120% of cost price.

17.

  • Answer: 85.71 litres (or 600/7 litres)
  • Working:
    • Let capacity = C litres
    • Initially: 2/5 C
    • After adding 30 litres: 3/4 C
    • 3/4 C - 2/5 C = 30
    • Common denominator: (15/20 - 8/20)C = 30
    • 7/20 C = 30
    • C = 30 × 20/7 = 600/7 ≈ 85.71 litres
  • Marking Notes: 1 mark for setting up equation, 1 mark for correct algebra, 1 mark for correct answer, 1 mark for clear working, 1 mark for correct units.
  • Teaching Note: The difference between the two fractions represents the 30 litres added.

18.

  • Answer: Length = 120 m, Speed = 8 m/s
  • Working:
    • Let length of train = L m, speed = v m/s
    • Passing a pole: distance = L, time = 15 s → L = 15v
    • Passing a platform: distance = L + 240, time = 45 s → L + 240 = 45v
    • Substitute: 15v + 240 = 45v
    • 30v = 240
    • v = 8 m/s
    • L = 15 × 8 = 120 m
  • Marking Notes: 1 mark for setting up first equation, 1 mark for setting up second equation, 1 mark for solving, 1 mark for correct speed, 1 mark for correct length.
  • Teaching Note: When a train passes a pole, the distance is the length of the train. When it passes a platform, the distance is the length of the train plus the length of the platform.

19.

  • Answer: 12 years old
  • Working:
    • Let son's age = x years
    • Man's age = 3x years
    • In 12 years: son = x + 12, man = 3x + 12
    • 3x + 12 = 2(x + 12)
    • 3x + 12 = 2x + 24
    • x = 12
    • Son is 12 years old now.
  • Marking Notes: 1 mark for setting up variables, 1 mark for setting up equation, 1 mark for solving, 1 mark for correct answer, 1 mark for clear working.
  • Teaching Note: This is an age problem. The key is to express both ages in terms of the son's current age.

20.

  • Answer: 3080 cm³
  • Working:
    • The longer side (44 cm) becomes the circumference of the base.
    • Circumference = 44 cm = 2πr
    • 2 × 22/7 × r = 44
    • r = 44 × 7 / (2 × 22) = 7 cm
    • Height of cylinder = width of paper = 20 cm
    • Volume = πr²h = 22/7 × 7² × 20 = 22/7 × 49 × 20 = 22 × 7 × 20 = 3080 cm³
  • Marking Notes: 1 mark for identifying circumference, 1 mark for finding radius, 1 mark for correct height, 1 mark for volume formula, 1 mark for final answer.
  • Teaching Note: When a rectangular paper is folded to form a cylinder, the longer side becomes the circumference of the base, and the shorter side becomes the height.