PSLE
In a school, 40% of the members in Literary Club and 45% of the members in Chess Club are boys. Both clubs have the same number of girls. The Chess Club has 15 more boys than the Literary Club. How many boys are there altogether?

	Literary Club		Chess Club
Types	Boys	Girls	Boys	Girls
Comparing the boys and the girls in each club	2x11	3x11	9x3	11x3
Comparing the girls in 2 clubs		1		1
	22 u	33 u	27 u	33 u

40% = ⁴⁰₁₀₀ = ²₅

Fraction of the members in Literary Club that are girls
= 1 - ²₅
= ³₅

45% = ⁴⁵₁₀₀ = ⁹₂₀

Fraction of the members in Chess club that are girls
= 1 - ⁹₂₀
= ¹¹₂₀

The number of girls in both clubs is the same. Make the numerators the same. LCM of 3 and 11 is 33. 

3x115x11 of the members in Literary Club = 11x320x3 of the members in Chess Club
3355of the members in Literary Club = 3360 of the members in Chess Club

Number of more boys in Chess Club than Literary Club
= 27 u - 22 u
= 5 u

5 u = 15

1 u = 15 ÷ 5 = 3

Total number of boys
= 22 u + 27 u
= 49 u
= 49 x 3
= 147

Answer(s): 147