PSLE
In a school, 40% of the members in Singing Club and 75% of the members in Dancing Club are girls. Both clubs have the same number of boys. The Dancing Club has 70 more girls than the Singing Club. How many girls are there altogether?

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

40% = ⁴⁰₁₀₀ = ²₅

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

75% = ⁷⁵₁₀₀ = ³₄

Fraction of the members in Dancing 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. 

3x15x1 of the members in Singing Club = 1x34x3 of the members in Dancing Club
35of the members in Singing Club = 312 of the members in Dancing Club

Number of more girls in Dancing Club than Singing Club
= 9 u - 2 u
= 7 u

7 u = 70

1 u = 70 ÷ 7 = 10

Total number of girls
= 2 u + 9 u
= 11 u
= 11 x 10
= 110

Answer(s): 110