PSLE
In a school, 40% of the members in Reading Club and 60% of the members in Computer Club are girls. Both clubs have the same number of boys. The Reading Club has 25 less girls than the Computer Club. How many members are there in Computer Club?

	Reading Club		Computer 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 Reading Club that are boys
= 1 - ²₅
= ³₅

60% = ⁶⁰₁₀₀ = ³₅

Fraction of the members in Computer 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 Reading Club = 2x35x3 of the members in Computer Club
610of the members in Reading Club = 615 of the members in Computer Club

Number of less girls in Reading Club than Computer Club
= 9 u - 4 u
= 5 u

5 u = 25

1 u = 25 ÷ 5 = 5

Number of members in Computer Club
= 15 u
= 15 x 5
= 75

Answer(s): 75