Audrey's school organized a trip to Peru. At first, the ratio of the number of boys to the number of girls who planned to participate in the trip was 8 : 7. On the day of registration, 32 girls decided to withdraw and 32 more boys decided to join in. In the end, the number of girls who participated became 20% of the total children for the trip. How many more boys than girls would visit Peru in the end?

	Boys	Girls	Total
Before	8x1 = 8 u	7x1 = 7 u	15x1 = 15 u
Change	+ 4 u	- 4 u
After	4x3 = 12 u	1x3 = 3 u	5x3 = 15 u

20% = ²⁰₁₀₀ = ¹₅

Since 32 girls withdrew and another 32 boys joined, the total number of children  at first and in the end remains unchanged. Make the total number of children the same. LCM of 15 and 5 is 15.

Number of girls who decided to withdraw
= 7 u - 3 u
= 4 u

4 u = 32

1 u = 32 ÷ 4 = 8

Number of more boys than girls in the end
= 12 u - 3 u
= 9 u
= 9 x 8
= 72

Answer(s): 72