This blog is managed by Song Hock Chye, author of Improve Your Thinking Skills in Maths (P1-P3 series), which is published and distributed by EPH.

## Monday, December 31, 2007

### Nan Hua Primary School PSLE Math Prelim 2006 (Q48)

X and Y are two schools in the same cluster. In school X, the ratio of the number of girls to the number of boys is 4 : 1. In school Y, the ratio of the number of girls to the number of boys is 2 : 3. School X has twice as many pupils as school Y.

a) Find the ratio of the number of girls in school X to the number of boys in school Y.

b) After 40 boys leave school X to join school Y, the ratio of the number of girls to the number of boys in school Y becomes 5 : 8. How many boys are there in school Y now?

Solution

Q(a)

Answer: The ratio of the number of girls in School X to the number of boys in School Y is 8 : 3.

Q(b)

40 boys from School X joined School Y

The number of units for boys increased by 1 unit from 15 to 16.

1 unit ----- 40 (boys transferred to School Y)

Total number of boys in School Y

16 units ----- 16 x 40 = 640

Answer: There are 640 boys in School Y now.