In a school, 0.75 of the boys and 0.3 of the girls take part in interviews. There is an equal number of girls and boys who do not take part in interviews. If 480 students take part in interviews, how many less students do not take part in interviews than those who take part in interviews?

Boys		Girls
Take part	Do not take part	Take part	Do not take part
3x7	1x7	3	7
	1x7		1x7
21 u	7 u	3 u	7 u

0.75 = ³₄
Boys that take part : Boys that do not take part = 3 : 1

0.3 = ³₁₀
Girls that take part : Girls that do not take part = 3 : 7

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 7 is 7.

Number of students who take part in interviews
= 21 u + 3 u
= 24 u

24 u = 480

1 u = 480 ÷ 24 = 20

Number of students who do not take part in interviews
= 7 u + 7 u
= 14 u

Number of less students who do not take part in interviews than those who take part in interviews
= 24 u - 14 u 
= 10 u
= 10 x 20
= 200

Answer(s): 200