In a school, 0.8 of the boys and 0.7 of the girls take part in competitions. There is an equal number of girls and boys who do not take part in competitions. If 78 pupils do not take part in competitions, how many more pupils take part in competitions than those who do not take part in competitions?

Boys		Girls
Take part	Do not take part	Take part	Do not take part
4x3	1x3	7	3
	1x3		1x3
12 u	3 u	7 u	3 u

0.8 = ⁴₅
Boys that take part : Boys that do not take part = 4 : 1

0.7 = ⁷₁₀
Girls that take part : Girls that do not take part = 7 : 3

The number of girls who do not take part is repeated.  Make the number of girls who do not take part the same.  LCM of 1 and 3 is 3.

Number of pupils who do not take part in competitions
= 3 u + 3 u
= 6 u

6 u = 78

1 u = 78 ÷ 6 = 13

Number of pupils who take part in competitions
= 12 u + 7 u
= 19 u

Number of more pupils who take part in competitions than those who do not take part in competitions
= 19 u - 6 u
= 13 u
= 13 x 13
= 169

Answer(s): 169