19 of the visitors at a bird park were girls. 80% of the remaining visitors were boys and the rest were adults. The total number of girls and adults is 323 less than the number of boys. After some boys entered the bird park, 80% of the visitors that remained were boys. How many boys entered the bird park?
Girls |
Adults |
Boys |
Total |
1x5 |
8x5 |
9x5 |
|
1x8 |
4x8 |
|
5 |
8 |
32 |
45 |
|
Girls and adults |
Boys |
Before |
13x1 = 13 u |
32x1 = 32 u |
Change |
|
+ 20 u |
After
|
1x13 = 13 u |
4x13 = 52 u |
80% =
80100 =
45 Adults : Boys = 1 : 4
The total number of adults and boys at first is repeated. Make the total number of adults at first the same. LCM of 8 and 5 is 40.
80% =
80100 =
45 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 13 and 1 is 13.
The total number of girls and adults is 323 less than the number of boys.
Number of less girls and adults than the number of boys at first
= 32 u - 13 u
= 19 u
19 u = 323
1 u = 323 ÷ 19 = 17
Number of boys who entered the bird park
= 52 u - 32 u
= 20 u
= 20 x 17
= 340
Answer(s): 340