Mason's school organized a trip to Australia. 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, 8 girls decided to withdraw and 8 more boys decided to join in. In the end, the number of girls who participated became 35% of the total children for the trip. How many more boys than girls would visit Australia in the end?

	Boys	Girls	Total
Before	7x5 = 35 u	5x5 = 25 u	12x5 = 60 u
Change	+ 4 u	- 4 u
After	13x3 = 39 u	7x3 = 21 u	20x3 = 60 u

35% = ³⁵₁₀₀ = ⁷₂₀

Since 8 girls withdrew and another 8 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 - 21 u
= 4 u

4 u = 8

1 u = 8 ÷ 4 = 2

Number of more boys than girls in the end
= 39 u - 21 u
= 18 u
= 18 x 2
= 36

Answer(s): 36