Christopher'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 10 : 9. On the day of registration, 156 girls decided to withdraw and 156 more boys decided to join in. In the end, the number of girls who participated became 20% of the total children for the trip. How many children would visit Brazil in the end?

	Boys	Girls	Total
Before	10x5 = 50 u	9x5 = 45 u	19x5 = 95 u
Change	+ 26 u	- 26 u
After	4x19 = 76 u	1x19 = 19 u	5x19 = 95 u

20% = ²⁰₁₀₀ = ¹₅

Since 156 girls withdrew and another 156 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 19 and 5 is 95.

Number of girls who decided to withdraw
= 45 u - 19 u
= 26 u

26 u = 156

1 u = 156 ÷ 26 = 6

Number of children that would visit Brazil in the end
= 76 u + 19 u
= 95 u
= 95 x 6
= 570

Answer(s): 570