PSLE
In a school, 70% of the members in Art Club and 90% of the members in Computer Club are boys. Both clubs have the same number of girls. The Computer Club has 60 more boys than the Art Club. How many boys are there altogether?

	Art Club		Computer Club
Types	Boys	Girls	Boys	Girls
Comparing the boys and the girls in each club	7x1	3x1	9x3	1x3
Comparing the girls in 2 clubs		1		1
	7 u	3 u	27 u	3 u

70% = ⁷⁰₁₀₀ = ⁷₁₀

Fraction of the members in Art Club that are girls
= 1 - ⁷₁₀
= ³₁₀

90% = ⁹⁰₁₀₀ = ⁹₁₀

Fraction of the members in Computer club that are girls
= 1 - ⁹₁₀
= ¹₁₀

The number of girls in both clubs is the same. Make the numerators the same. LCM of 3 and 1 is 3. 

3x110x1 of the members in Art Club = 1x310x3 of the members in Computer Club
310of the members in Art Club = 330 of the members in Computer Club

Number of more boys in Computer Club than Art Club
= 27 u - 7 u
= 20 u

20 u = 60

1 u = 60 ÷ 20 = 3

Total number of boys
= 7 u + 27 u
= 34 u
= 34 x 3
= 102

Answer(s): 102