315 people went to a zoo.
45 were children. Some adults joined halfway and the ratio of the number of children to the number of adults became 12 : 5. How many adults joined the zoo halfway?
| |
Children |
Adults |
Total |
| Before |
4x3 =
12 u |
1x3 =
3 u |
5x3 =
15 u |
| Change |
|
+ ? |
|
| After |
12 u |
5 u |
|
Fraction of the people that were adults at first
= 1 -
45 =
15 Number of children remains unchanged. Make the number of children the same. LCM of 4 and 12 is 12.
Total number of people at first = 15 u
15 u = 315
1 u = 315 ÷ 15 = 21
Number of adults who joined halfway
= 5 u - 3 u
= 2 u
= 2 x 21
= 42
Answer(s): 42
