19 of the visitors at a bird park were boys. 70% of the remaining visitors were girls and the rest were adults. The total number of boys and adults is 165 less than the number of girls. After some girls entered the bird park, 80% of the visitors that remained were girls. How many girls entered the bird park?
Boys |
Adults |
Girls |
Total |
1x5 |
8x5 |
9x5 |
|
3x4 |
7x4 |
|
5 |
12 |
28 |
45 |
|
Boys and adults |
Girls |
Before |
17x1 = 17 u |
28x1 = 28 u |
Change |
|
+ 40 u |
After
|
1x17 = 17 u |
4x17 = 68 u |
70% =
70100 =
710 Adults : Girls = 3 : 7
The total number of adults and girls at first is repeated. Make the total number of adults at first the same. LCM of 8 and 10 is 40.
80% =
80100 =
45 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 17 and 1 is 17.
The total number of boys and adults is 165 less than the number of girls.
Number of less boys and adults than the number of girls at first
= 28 u - 17 u
= 11 u
11 u = 165
1 u = 165 ÷ 11 = 15
Number of girls who entered the bird park
= 68 u - 28 u
= 40 u
= 40 x 15
= 600
Answer(s): 600