In a school, 0.8 of the boys and 0.7 of the girls take part in charity work. There is an equal number of girls and boys who do not take part in charity work. If 84 children do not take part in charity work, how many more children take part in charity work than those who do not take part in charity work?

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 children who do not take part in charity work
= 3 u + 3 u
= 6 u

6 u = 84

1 u = 84 ÷ 6 = 14

Number of children who take part in charity work
= 12 u + 7 u
= 19 u

Number of more children who take part in charity work than those who do not take part in charity work
= 19 u - 6 u
= 13 u
= 13 x 14
= 182

Answer(s): 182