Elizabeth's school organized a trip to Brazil. 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, 144 girls decided to withdraw and 144 more boys decided to join in. In the end, the number of girls who participated became 15% of the total children for the trip. How many children would visit Brazil in the end?

	Boys	Girls	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 144 girls withdrew and another 144 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 20 is 60.

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

16 u = 144

1 u = 144 ÷ 16 = 9

Number of children that would visit Brazil in the end
= 51 u + 9 u
= 60 u
= 60 x 9
= 540

Answer(s): 540