PSLE
In a school, 30% of the members in Dancing Club and 80% of the members in Singing Club are girls. Both clubs have the same number of boys. The Dancing Club has 75 less girls than the Singing Club. How many members are there in Singing Club?

	Dancing Club		Singing Club
Types	Girls	Boys	Girls	Boys
Comparing the girls and the boys in each club	3x1	7x1	4x7	1x7
Comparing the boys in 2 clubs		1		1
	3 u	7 u	28 u	7 u

30% = ³⁰₁₀₀ = ³₁₀

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

80% = ⁸⁰₁₀₀ = ⁴₅

Fraction of the members in Singing club that are boys
= 1 - ⁴₅
= ¹₅

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

7x110x1 of the members in Dancing Club = 1x75x7 of the members in Singing Club
710of the members in Dancing Club = 735 of the members in Singing Club

Number of less girls in Dancing Club than Singing Club
= 28 u - 3 u
= 25 u

25 u = 75

1 u = 75 ÷ 25 = 3

Number of members in Singing Club
= 35 u
= 35 x 3
= 105

Answer(s): 105