PSLE
On Thursday, the number of adults to girls to boys visiting a tourist attraction was 7 : 12 : 12. On Friday, the number of adults visiting the tourist attraction remained the same. However, the number of girls decreased by 25% and the number of boys increased by 25%.

1. What was the ratio of the number of children to adults visiting the tourist attraction on Friday?
2. On Thursday, 840 girls and boys visited the tourist attraction. What was the total number of child visitors at the tourist attraction on Friday?

	Adults	Girls	Boys
Before	7 u	12 u	12 u
Change		- 3 u	+ 3 u
After	7 u	9 u	15 u

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

Decrease in the number of boys
= 25% x 12 u
= ²⁵₁₀₀ x 12 u
= 3 u

Number of girls on Friday
= 12 u - 3 u
= 9 u

Number of boys on Friday
= 12 u + 3 u
= 15 u

Number of children on Friday
= 9 u + 15 u
= 24 u

On Friday
Children : Adults
24 : 7

(b)
Number of girls and boys on Thursday
= 12 u + 12 u
= 24 u

24 u = 840

1 u = 840 ÷ 24 = 35

Total number of child visitors on Friday
= 24 u
= 24 x 35
= 840

Answer(s): (a) 24 : 7; (b) 840