210 people went to a park.
57 were children. Some adults left halfway and the ratio of the number of children to the number of adults became 15 : 4. How many adults left the park halfway?
|
Children |
Adults |
Total |
Before |
5x3 = 15 u |
2x3 = 6 u |
7x3 = 21 u |
Change |
|
- ? |
|
After |
15 u |
4 u |
|
Fraction of the people that were adults at first
= 1 -
57 =
27 Number of children remains unchanged. Make the number of children the same. LCM of 5 and 15 is 15.
Total number of people at first = 21 u
21 u = 210
1 u = 210 ÷ 21 = 10
Number of adults who left halfway
= 6 u - 4 u
= 2 u
= 2 x 10
= 20
Answer(s): 20