840 people went to a zoo.
37 were children. Some adults left halfway and the ratio of the number of children to the number of adults became 12 : 13. How many adults left the zoo halfway?
| |
Children |
Adults |
Total |
| Before |
3x4 =
12 u |
4x4 =
16 u |
7x4 =
28 u |
| Change |
|
- ? |
|
| After |
12 u |
13 u |
|
Fraction of the people that were adults at first
= 1 -
37 =
47 Number of children remains unchanged. Make the number of children the same. LCM of 3 and 12 is 12.
Total number of people at first = 28 u
28 u = 840
1 u = 840 ÷ 28 = 30
Number of adults who left halfway
= 16 u - 13 u
= 3 u
= 3 x 30
= 90
Answer(s): 90
