In a school, the ratio of adults to the number of children is 10 : 3.
The ratio of the number of girls to the number of boys is 7 : 5.
There are 20 more girls than boys.
How many people are there in the school?
| Adults |
Children |
| 10 x 4 |
3 x 4 |
| |
Girls |
Boys |
| |
7 x 1 |
5 x 1 |
| 40 u |
7 u |
5 u |
The number of children is the combined repeated identity.
Make the number of children the same using the LCM of 3 and 12.
LCM of 3 and 12 = 12
Number of more girls than boys
= 7 u - 5 u
= 2 u
2 u = 20
1 u = 20 ÷ 2 = 10
Number of people
= 40 u + 7 u + 5 u
= 52 u
= 52 x 10
= 520
Answer(s): 520
