In a school, the ratio of adults to the number of children is 8 : 9.
The ratio of the number of boys to the number of girls is 7 : 5.
There are 30 less girls than boys.
How many people are there in the school?
| Adults |
Children |
| 8 x 4 |
9 x 4 |
| |
Boys |
Girls |
| |
7 x 3 |
5 x 3 |
| 32 u |
21 u |
15 u |
The number of children is the combined repeated identity.
Make the number of children the same using the LCM of 9 and 12.
LCM of 9 and 12 = 36
Number of less girls than boys
= 21 u - 15 u
= 6 u
6 u = 30
1 u = 30 ÷ 6 = 5
Number of people
= 32 u + 21 u + 15 u
= 68 u
= 68 x 5
= 340
Answer(s): 340
