PSLE Mathematics Problem Solving 4

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?

Accepted Answer

20

Answer

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?

Accepted Answer

8

Answer

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?

Accepted Answer

25

Answer

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?

Accepted Answer

54 cm²

Answer

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?

Accepted Answer

$110

Answer

After giving $20: both have $180 ÷ 2 = $90. So Priya originally had $90 + $20 = $110.

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