PSLE Mathematics Problem Solving 4 — Questions and Answers
Question 1: A man is 4 times as old as his son. In 10 years, the man will be 3 times as old as his son. How old is the son now?
- 15
- 20 (Correct answer)
- 10
- 25
Correct answer: 20
Let son's age = x. Man's age = 4x. In 10 years: 4x + 10 = 3(x + 10). 4x + 10 = 3x + 30. x = 20.
Question 2: A container has a capacity of 2.5 litres. How many such containers are needed to hold 18 litres of juice?
- 7
- 8 (Correct answer)
- 9
- 6
Correct answer: 8
18 ÷ 2.5 = 7.2. Since you cannot use a fraction of a container, you need 8 containers.
Question 3: The average of four numbers is 25. Three of the numbers are 18, 27, and 30. What is the fourth number?
- 20
- 25 (Correct answer)
- 22
- 28
Correct answer: 25
Total of 4 numbers = 25 × 4 = 100. Sum of three numbers = 18 + 27 + 30 = 75. Fourth number = 100 − 75 = 25.
Question 4: A triangle has a base of 12 cm and a height of 9 cm. What is its area?
- 108 cm²
- 54 cm² (Correct answer)
- 42 cm²
- 21 cm²
Correct answer: 54 cm²
Area of triangle = 1/2 × base × height = 1/2 × 12 × 9 = 54 cm².
Question 5: Priya and Raj have $180 altogether. If Priya gives Raj $20, they will have the same amount. How much does Priya have originally?
- $100
- $110 (Correct answer)
- $90
- $120
Correct answer: $110
After giving $20: both have $180 ÷ 2 = $90. So Priya originally had $90 + $20 = $110.
Question 6: A fruit seller had 2,400 oranges. He sold 3/8 of them on Day 1 and 5/12 of the remainder on Day 2. How many oranges were left?
- 875 (Correct answer)
- 900
- 750
- 1,000
Correct answer: 875
Day 1 sold: 3/8 × 2,400 = 900. Remainder = 1,500. Day 2 sold: 5/12 × 1,500 = 625. Left: 1,500 − 625 = 875.
PSLE Mathematics Problem Solving 4
A man is 4 times as old as his son.
In 10 years, the man will be 3 times as old as his son.
How old is the son now?