PSLE
On Saturday, the number of adults to girls to boys visiting a fun fair was 1 : 10 : 10. On Sunday, the number of adults visiting the fun fair remained the same. However, the number of girls increased by 10% and the number of boys decreased by 10%.

1. What was the ratio of the number of adults to girls to boys visiting the fun fair on Sunday?
2. On Saturday, 640 girls and boys visited the fun fair. What was the total number of visitors at the fun fair on Sunday?

	Adults	Girls	Boys
Before	1 u	10 u	10 u
Change		+ 1 u	- 1 u
After	1 u	11 u	9 u

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

Decrease in the number of boys
= 10% x 10 u
= ¹⁰₁₀₀ x 10 u
= 1 u

Number of girls on Sunday
= 10 u + 1 u
= 11 u

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

On Sunday
Adults : Girls : Boys
1 : 11 : 9

(b)
Number of girls and boys on Saturday
= 10 u + 10 u
= 20 u

20 u = 640

1 u = 640 ÷ 20 = 32

Total number of visitors on Sunday
= 1 u + 11 u + 9 u
= 21 u
= 21 x 32
= 672

Answer(s): (a) 1 : 11 : 9; (b) 672