PSLE
In a school, 30% of the members in Chess Club and 75% of the members in Literary Club are boys. Both clubs have the same number of girls. The Chess Club has 72 less boys than the Literary Club. How many members are there in Literary Club?

	Chess Club		Literary Club
Types	Boys	Girls	Boys	Girls
Comparing the boys and the girls in each club	3x1	7x1	3x7	1x7
Comparing the girls in 2 clubs		1		1
	3 u	7 u	21 u	7 u

30% = ³⁰₁₀₀ = ³₁₀

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

75% = ⁷⁵₁₀₀ = ³₄

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

The number of girls in both clubs is the same. Make the numerators the same. LCM of 7 and 1 is 7. 

7x110x1 of the members in Chess Club = 1x74x7 of the members in Literary Club
710of the members in Chess Club = 728 of the members in Literary Club

Number of less boys in Chess Club than Literary Club
= 21 u - 3 u
= 18 u

18 u = 72

1 u = 72 ÷ 18 = 4

Number of members in Literary Club
= 28 u
= 28 x 4
= 112

Answer(s): 112