PSLE
On Wednesday, the number of adults to boys to girls visiting a bird park was 1 : 10 : 10. On Thursday, the number of adults visiting the bird park remained the same. However, the number of boys increased by 30% and the number of girls decreased by 10%.

1. What was the ratio of the number of adults to boys to girls visiting the bird park on Thursday?
2. On Wednesday, 720 boys and girls visited the bird park. What was the total number of visitors at the bird park on Thursday?

	Adults	Boys	Girls
Before	1 u	10 u	10 u
Change		+ 3 u	- 1 u
After	1 u	13 u	9 u

(a)
Increase in the number of boys
= 30% x 10 u
= ³⁰₁₀₀ x 10 u
= 3 u

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

Number of boys on Thursday
= 10 u + 3 u
= 13 u

Number of girls on Thursday
= 10 u - 1 u
= 9 u

On Thursday
Adults : Boys : Girls
1 : 13 : 9

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

20 u = 720

1 u = 720 ÷ 20 = 36

Total number of visitors on Thursday
= 1 u + 13 u + 9 u
= 23 u
= 23 x 36
= 828

Answer(s): (a) 1 : 13 : 9; (b) 828