630 people went to a concert hall.
37 were adults. Some children joined halfway and the ratio of the number of adults to the number of children became 9 : 16. How many children joined the concert hall halfway?
| |
Adults |
Children |
Total |
| Before |
3x3 =
9 u |
4x3 =
12 u |
7x3 =
21 u |
| Change |
|
+ ? |
|
| After |
9 u |
16 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 = 630
1 u = 630 ÷ 21 = 30
Number of children who joined halfway
= 16 u - 12 u
= 4 u
= 4 x 30
= 120
Answer(s): 120
