PSLE
On Monday, the number of adults to boys to girls visiting a safari park was 1 : 2 : 2. On Tuesday, the number of adults visiting the safari park remained the same. However, the number of boys increased by 50% and the number of girls decreased by 50%.

1. What was the ratio of the number of adults to boys to girls visiting the safari park on Tuesday?
2. On Monday, 180 boys and girls visited the safari park. What was the total number of visitors at the safari park on Tuesday?

	Adults	Boys	Girls
Before	1 u	2 u	2 u
Change		+ 1 u	- 1 u
After	1 u	3 u	1 u

(a)
Increase in the number of boys
= 50% x 2 u
= ⁵⁰₁₀₀ x 2 u
= 1 u

Decrease in the number of girls
= 50% x 2 u
= ⁵⁰₁₀₀ x 2 u
= 1 u

Number of boys on Tuesday
= 2 u + 1 u
= 3 u

Number of girls on Tuesday
= 2 u - 1 u
= 1 u

On Tuesday
Adults : Boys : Girls
1 : 3 : 1

(b)
Number of boys and girls on Monday
= 2 u + 2 u
= 4 u

4 u = 180

1 u = 180 ÷ 4 = 45

Total number of visitors on Tuesday
= 1 u + 3 u + 1 u
= 5 u
= 5 x 45
= 225

Answer(s): (a) 1 : 3 : 1; (b) 225