399 people went to a zoo.
37 were adults. Some children left halfway and the ratio of the number of adults to the number of children became 9 : 10. How many children left the zoo halfway?
| |
Adults |
Children |
Total |
| Before |
3x3 =
9 u |
4x3 =
12 u |
7x3 =
21 u |
| Change |
|
- ? |
|
| After |
9 u |
10 u |
|
Fraction of the people that were children at first
= 1 -
37 =
47 Number of adults remains unchanged. Make the number of adults the same. LCM of 3 and 9 is 9.
Total number of people at first = 21 u
21 u = 399
1 u = 399 ÷ 21 = 19
Number of children who left halfway
= 12 u - 10 u
= 2 u
= 2 x 19
= 38
Answer(s): 38
