580 people went to a concert hall.
25 were adults. Some children joined halfway and the ratio of the number of adults to the number of children became 8 : 15. How many children joined the concert hall halfway?
| |
Adults |
Children |
Total |
| Before |
2x4 =
8 u |
3x4 =
12 u |
5x4 =
20 u |
| Change |
|
+ ? |
|
| After |
8 u |
15 u |
|
Fraction of the people that were children at first
= 1 -
25 =
35 Number of adults remains unchanged. Make the number of adults the same. LCM of 2 and 8 is 8.
Total number of people at first = 20 u
20 u = 580
1 u = 580 ÷ 20 = 29
Number of children who joined halfway
= 15 u - 12 u
= 3 u
= 3 x 29
= 87
Answer(s): 87
