In a school, 0.9 of the girls and 0.1 of the boys take part in charity work. There is an equal number of boys and girls who do not take part in charity work. If 324 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?

Girls		Boys
Take part	Do not take part	Take part	Do not take part
9x9	1x9	1	9
	1x9		1x9
81 u	9 u	1 u	9 u

0.9 = ⁹₁₀
Girls that take part : Girls that do not take part = 9 : 1

0.1 = ¹₁₀
Boys that take part : Boys that do not take part = 1 : 9

The number of boys who do not take part is repeated.  Make the number of boys who do not take part the same.  LCM of 1 and 9 is 9.

Number of children who do not take part in charity work
= 9 u + 9 u
= 18 u

18 u = 324

1 u = 324 ÷ 18 = 18

Number of children who take part in charity work
= 81 u + 1 u
= 82 u

Number of more children who take part in charity work than those who do not take part in charity work
= 82 u - 18 u
= 64 u
= 64 x 18
= 1152

Answer(s): 1152