Emma's school organized a trip to Oman. At first, the ratio of the number of girls to the number of boys who planned to participate in the trip was 8 : 7. On the day of registration, 40 boys decided to withdraw and 40 more girls decided to join in. In the end, the number of boys who participated became 20% of the total children for the trip. How many more girls than boys would visit Oman in the end?

	Girls	Boys	Total
Before	8x1 = 8 u	7x1 = 7 u	15x1 = 15 u
Change	+ 4 u	- 4 u
After	4x3 = 12 u	1x3 = 3 u	5x3 = 15 u

20% = ²⁰₁₀₀ = ¹₅

Since 40 boys withdrew and another 40 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 15 and 5 is 15.

Number of boys who decided to withdraw
= 7 u - 3 u
= 4 u

4 u = 40

1 u = 40 ÷ 4 = 10

Number of more girls than boys in the end
= 12 u - 3 u
= 9 u
= 9 x 10
= 90

Answer(s): 90