18 of the visitors at a safari park were girls. 75% of the remaining visitors were boys and the rest were adults. The total number of girls and adults is 150 less than the number of boys. After some boys entered the safari park, 75% of the visitors that remained were boys. How many boys entered the safari park?
Girls |
Adults |
Boys |
Total |
1x4 |
7x4 |
8x4 |
|
1x7 |
3x7 |
|
4 |
7 |
21 |
32 |
|
Girls and adults |
Boys |
Before |
11x1 = 11 u |
21x1 = 21 u |
Change |
|
+ 12 u |
After
|
1x11 = 11 u |
3x11 = 33 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 7 and 4 is 28.
75% =
75100 =
34 When some boys entered, the total number of girls and adults remains unchanged. Make the total number of girls and adults the same. LCM of 11 and 1 is 11.
The total number of girls and adults is 150 less than the number of boys.
Number of less girls and adults than the number of boys at first
= 21 u - 11 u
= 10 u
10 u = 150
1 u = 150 ÷ 10 = 15
Number of boys who entered the safari park
= 33 u - 21 u
= 12 u
= 12 x 15
= 180
Answer(s): 180