Tommy's school organized a trip to Iraq. At first, the ratio of the number of girls to the number of boys who planned to participate in the trip was 10 : 9. On the day of registration, 170 boys decided to withdraw and 170 more girls decided to join in. In the end, the number of boys who participated became 25% of the total children for the trip. How many less boys than girls would visit Iraq in the end?

	Girls	Boys	Total
Before	10x4 = 40 u	9x4 = 36 u	19x4 = 76 u
Change	+ 17 u	- 17 u
After	3x19 = 57 u	1x19 = 19 u	4x19 = 76 u

25% = ²⁵₁₀₀ = ¹₄

Since 170 boys withdrew and another 170 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 19 and 4 is 76.

Number of boys who decided to withdraw
= 36 u - 19 u
= 17 u

17 u = 170

1 u = 170 ÷ 17 = 10

Number of less boys than girls in the end
= 57 u - 19 u
= 38 u
= 38 x 10
= 380

Answer(s): 380