Lily's school organized a trip to Sweden. At first, the ratio of the number of girls to the number of boys who planned to participate in the trip was 7 : 5. On the day of registration, 64 boys decided to withdraw and 64 more girls decided to join in. In the end, the number of boys who participated became 15% of the total children for the trip. How many children would visit Sweden in the end?

	Girls	Boys	Total
Before	7x5 = 35 u	5x5 = 25 u	12x5 = 60 u
Change	+ 16 u	- 16 u
After	17x3 = 51 u	3x3 = 9 u	20x3 = 60 u

15% = ¹⁵₁₀₀ = ³₂₀

Since 64 boys withdrew and another 64 girls 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 20 is 60.

Number of boys who decided to withdraw
= 25 u - 9 u
= 16 u

16 u = 64

1 u = 64 ÷ 16 = 4

Number of children that would visit Sweden in the end
= 51 u + 9 u
= 60 u
= 60 x 4
= 240

Answer(s): 240