PSLE
In a school, 45% of the members in Dancing Club and 60% of the members in Singing Club are girls. Both clubs have the same number of boys. The Singing Club has 30 more girls than the Dancing Club. How many girls are there altogether?

	Dancing Club		Singing Club
Types	Girls	Boys	Girls	Boys
Comparing the girls and the boys in each club	9x2	11x2	3x11	2x11
Comparing the boys in 2 clubs		1		1
	18 u	22 u	33 u	22 u

45% = ⁴⁵₁₀₀ = ⁹₂₀

Fraction of the members in Dancing Club that are boys
= 1 - ⁹₂₀
= ¹¹₂₀

60% = ⁶⁰₁₀₀ = ³₅

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

The number of boys in both clubs is the same. Make the numerators the same. LCM of 11 and 2 is 22. 

11x220x2 of the members in Dancing Club = 2x115x11 of the members in Singing Club
2240of the members in Dancing Club = 2255 of the members in Singing Club

Number of more girls in Singing Club than Dancing Club
= 33 u - 18 u
= 15 u

15 u = 30

1 u = 30 ÷ 15 = 2

Total number of girls
= 18 u + 33 u
= 51 u
= 51 x 2
= 102

Answer(s): 102