Christian's school organized a trip to Japan. 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, 20 girls decided to withdraw and 20 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 less girls than boys would visit Japan 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 20 girls withdrew and another 20 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 = 20

1 u = 20 ÷ 2 = 10

Number of less girls than boys in the end
= 9 u - 3 u
= 6 u
= 6 x 10
= 60

Answer(s): 60