PSLE
In a school, 70% of the members in Literary Club and 80% of the members in Chess Club are boys. Both clubs have the same number of girls. The Literary Club has 50 less boys than the Chess Club. How many members are there in Chess Club?

	Literary Club		Chess Club
Types	Boys	Girls	Boys	Girls
Comparing the boys and the girls in each club	7x1	3x1	4x3	1x3
Comparing the girls in 2 clubs		1		1
	7 u	3 u	12 u	3 u

70% = ⁷⁰₁₀₀ = ⁷₁₀

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

80% = ⁸⁰₁₀₀ = ⁴₅

Fraction of the members in Chess club that are girls
= 1 - ⁴₅
= ¹₅

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 Literary Club = 1x35x3 of the members in Chess Club
310of the members in Literary Club = 315 of the members in Chess Club

Number of less boys in Literary Club than Chess Club
= 12 u - 7 u
= 5 u

5 u = 50

1 u = 50 ÷ 5 = 10

Number of members in Chess Club
= 15 u
= 15 x 10
= 150

Answer(s): 150