¹₁₀ of the visitors at a zoo were girls. 75% of the remaining visitors were boys and the rest were adults. The number of boys was 448 more than the total number of girls and adults. After some boys left the zoo, 60% of the visitors that remained were boys. How many boys left the zoo?

Girls	Adults	Boys	Total
1x4	9x4		10x4
	1x9	3x9
4	9	27	40

	Girls and adults	Boys
Before	13x2 = 26 u	27x2 = 54 u
Change		- 15 u
After	2x13 = 26 u	3x13 = 39 u

75% = ⁷⁵₁₀₀ = ³₄
Adults : Boys = 1 : 3

The total number of adults and boys at first is repeated.  Make the total number of adults at first the same. LCM of 9 and 4 is 36.

60% = ⁶⁰₁₀₀ = ³₅

When some boys left, the total number of girls and adults remains unchanged. Make the total number of girls and adults the same. LCM of 13 and 2 is 26.

The number of boys was 448 more than the total number of girls and adults at first.

Number of more boys than the total number of girls and adults at first
= 54 u - 26 u
= 28 u

28 u = 448

1 u = 448 ÷ 28 = 16

Number of boys who left the zoo
= 54 u - 39 u
= 15 u
= 15 x 16
= 240

Answer(s): 240