PSLE
On Wednesday, the number of adults to girls to boys visiting a fun fair was 3 : 12 : 8. On Thursday, the number of adults visiting the fun fair remained the same. However, the number of girls increased by 25% and the number of boys decreased by 50%.

1. What was the ratio of the number of adults to girls to boys visiting the fun fair on Thursday?
2. On Wednesday, 780 girls and boys visited the fun fair. What was the total number of visitors at the fun fair on Thursday?

	Adults	Girls	Boys
Before	3 u	12 u	8 u
Change		+ 3 u	- 4 u
After	3 u	15 u	4 u

(a)
Increase in the number of girls
= 25% x 12 u
= ²⁵₁₀₀ x 12 u
= 3 u

Decrease in the number of boys
= 50% x 8 u
= ⁵⁰₁₀₀ x 8 u
= 4 u

Number of girls on Thursday
= 12 u + 3 u
= 15 u

Number of boys on Thursday
= 8 u - 4 u
= 4 u

On Thursday
Adults : Girls : Boys
3 : 15 : 4

(b)
Number of girls and boys on Wednesday
= 12 u + 8 u
= 20 u

20 u = 780

1 u = 780 ÷ 20 = 39

Total number of visitors on Thursday
= 3 u + 15 u + 4 u
= 22 u
= 22 x 39
= 858

Answer(s): (a) 3 : 15 : 4; (b) 858