PSLE
On Tuesday, the number of adults to boys to girls visiting a bird park was 7 : 8 : 4. On Wednesday, the number of adults visiting the bird park remained the same. However, the number of boys decreased by 25% and the number of girls increased by 25%.

1. What was the ratio of the number of children to adults visiting the bird park on Wednesday?
2. On Tuesday, 540 boys and girls visited the bird park. What was the total number of child visitors at the bird park on Wednesday?

	Adults	Boys	Girls
Before	7 u	8 u	4 u
Change		- 2 u	+ 1 u
After	7 u	6 u	5 u

(a)
Increase in the number of boys
= 25% x 8 u
= ²⁵₁₀₀ x 8 u
= 2 u

Decrease in the number of girls
= 25% x 4 u
= ²⁵₁₀₀ x 4 u
= 1 u

Number of boys on Wednesday
= 8 u - 2 u
= 6 u

Number of girls on Wednesday
= 4 u + 1 u
= 5 u

Number of children on Wednesday
= 6 u + 5 u
= 11 u

On Wednesday
Children : Adults
11 : 7

(b)
Number of boys and girls on Tuesday
= 8 u + 4 u
= 12 u

12 u = 540

1 u = 540 ÷ 12 = 45

Total number of child visitors on Wednesday
= 11 u
= 11 x 45
= 495

Answer(s): (a) 11 : 7; (b) 495