PSLE
In a school, 40% of the members in Singing Club and 60% of the members in Dancing Club are girls. Both clubs have the same number of boys. The Singing Club has 15 less girls than the Dancing Club. How many members are there in Dancing Club?

	Singing Club		Dancing Club
Types	Girls	Boys	Girls	Boys
Comparing the girls and the boys in each club	2x2	3x2	3x3	2x3
Comparing the boys in 2 clubs		1		1
	4 u	6 u	9 u	6 u

40% = ⁴⁰₁₀₀ = ²₅

Fraction of the members in Singing Club that are boys
= 1 - ²₅
= ³₅

60% = ⁶⁰₁₀₀ = ³₅

Fraction of the members in Dancing club that are boys
= 1 - ³₅
= ²₅

The number of boys in both clubs is the same. Make the numerators the same. LCM of 3 and 2 is 6. 

3x25x2 of the members in Singing Club = 2x35x3 of the members in Dancing Club
610of the members in Singing Club = 615 of the members in Dancing Club

Number of less girls in Singing Club than Dancing Club
= 9 u - 4 u
= 5 u

5 u = 15

1 u = 15 ÷ 5 = 3

Number of members in Dancing Club
= 15 u
= 15 x 3
= 45

Answer(s): 45