Oliver's school organized a trip to Thailand. At first, the ratio of the number of boys to the number of girls who planned to participate in the trip was 7 : 5. On the day of registration, 12 girls decided to withdraw and 12 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 more boys than girls would visit Thailand in the end?

	Boys	Girls	Total
Before	7x1 = 7 u	5x1 = 5 u	12x1 = 12 u
Change	+ 2 u	- 2 u
After	3x3 = 9 u	1x3 = 3 u	4x3 = 12 u

25% = ²⁵₁₀₀ = ¹₄

Since 12 girls withdrew and another 12 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 12 and 4 is 12.

Number of girls who decided to withdraw
= 5 u - 3 u
= 2 u

2 u = 12

1 u = 12 ÷ 2 = 6

Number of more boys than girls in the end
= 9 u - 3 u
= 6 u
= 6 x 6
= 36

Answer(s): 36