¹₈ of the people at a park were boys. 80% of the remaining people were girls and the rest were adults. The total number of boys and adults is 288 less than the number of girls. After some girls entered the park, 75% of the people that remained were girls. How many girls entered the park?

Boys	Adults	Girls	Total
1x5	7x5		8x5
	1x7	4x7
5	7	28	40

	Boys and adults	Girls
Before	12x1 = 12 u	28x1 = 28 u
Change		+ 8 u
After	1x12 = 12 u	3x12 = 36 u

80% = ⁸⁰₁₀₀ = ⁴₅
Adults : Girls = 1 : 4

The total number of adults and girls at first is repeated.  Make the total number of adults at first the same. LCM of 7 and 5 is 35.

75% = ⁷⁵₁₀₀ = ³₄

When some girls entered, the total number of boys and adults remains unchanged. Make the total number of boys and adults the same. LCM of 12 and 1 is 12.

The total number of boys and adults is 288 less than the number of girls.

Number of less boys and adults than the number of girls at first
= 28 u - 12 u
= 16 u

16 u = 288

1 u = 288 ÷ 16 = 18

Number of girls who entered the park
= 36 u - 28 u
= 8 u
= 8 x 18
= 144

Answer(s): 144