PSLE
In a school, 70% of the members in Literary Club and 75% of the members in Chess Club are girls. Both clubs have the same number of boys. The Chess Club has 4 more girls than the Literary Club. How many girls are there altogether?

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

70% = ⁷⁰₁₀₀ = ⁷₁₀

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

75% = ⁷⁵₁₀₀ = ³₄

Fraction of the members in Chess club that are boys
= 1 - ³₄
= ¹₄

The number of boys 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 = 1x34x3 of the members in Chess Club
310of the members in Literary Club = 312 of the members in Chess Club

Number of more girls in Chess Club than Literary Club
= 9 u - 7 u
= 2 u

2 u = 4

1 u = 4 ÷ 2 = 2

Total number of girls
= 7 u + 9 u
= 16 u
= 16 x 2
= 32

Answer(s): 32