Luke'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 : 5. On the day of registration, 42 girls decided to withdraw and 42 more boys decided to join in. In the end, the number of girls who participated became 25% of the total children for the trip. How many children would visit Peru in the end?

	Boys	Girls	Total
Before	8x4 = 32 u	5x4 = 20 u	13x4 = 52 u
Change	+ 7 u	- 7 u
After	3x13 = 39 u	1x13 = 13 u	4x13 = 52 u

25% = ²⁵₁₀₀ = ¹₄

Since 42 girls withdrew and another 42 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 13 and 4 is 52.

Number of girls who decided to withdraw
= 20 u - 13 u
= 7 u

7 u = 42

1 u = 42 ÷ 7 = 6

Number of children that would visit Peru in the end
= 39 u + 13 u
= 52 u
= 52 x 6
= 312

Answer(s): 312