PSLE
On Saturday, the number of adults to boys to girls visiting a fun fair was 3 : 10 : 5. On Sunday, the number of adults visiting the fun fair remained the same. However, the number of boys decreased by 10% and the number of girls increased by 20%.

1. What was the ratio of the number of children to adults visiting the fun fair on Sunday?
2. On Saturday, 420 boys and girls visited the fun fair. What was the total number of child visitors at the fun fair on Sunday?

	Adults	Boys	Girls
Before	3 u	10 u	5 u
Change		- 1 u	+ 1 u
After	3 u	9 u	6 u

(a)
Increase in the number of boys
= 10% x 10 u
= ¹⁰₁₀₀ x 10 u
= 1 u

Decrease in the number of girls
= 20% x 5 u
= ²⁰₁₀₀ x 5 u
= 1 u

Number of boys on Sunday
= 10 u - 1 u
= 9 u

Number of girls on Sunday
= 5 u + 1 u
= 6 u

Number of children on Sunday
= 9 u + 6 u
= 15 u

On Sunday
Children : Adults
15 : 3

(b)
Number of boys and girls on Saturday
= 10 u + 5 u
= 15 u

15 u = 420

1 u = 420 ÷ 15 = 28

Total number of child visitors on Sunday
= 15 u
= 15 x 28
= 420

Answer(s): (a) 15 : 3; (b) 420