PSLE
In a school, 70% of the members in Art Club and 75% of the members in Computer Club are boys. Both clubs have the same number of girls. The Art Club has 6 less boys than the Computer Club. How many members are there in Computer Club?

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

70% = ⁷⁰₁₀₀ = ⁷₁₀

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

75% = ⁷⁵₁₀₀ = ³₄

Fraction of the members in Computer club that are girls
= 1 - ³₄
= ¹₄

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 = 1x34x3 of the members in Computer Club
310of the members in Art Club = 312 of the members in Computer Club

Number of less boys in Art Club than Computer Club
= 9 u - 7 u
= 2 u

2 u = 6

1 u = 6 ÷ 2 = 3

Number of members in Computer Club
= 12 u
= 12 x 3
= 36

Answer(s): 36