In a school, the ratio of adults to the number of children is 7 : 2.
The ratio of the number of boys to the number of girls is 5 : 4.
There are 90 less girls than boys.
How many people are there in the school?
Adults |
Children |
7 x 9 |
2 x 9 |
|
Boys |
Girls |
|
5 x 2 |
4 x 2 |
63 u |
10 u |
8 u |
The number of children is the combined repeated identity.
Make the number of children the same using the LCM of 2 and 9.
LCM of 2 and 9 = 18
Number of less girls than boys
= 10 u - 8 u
= 2 u
2 u = 90
1 u = 90 ÷ 2 = 45
Number of people
= 63 u + 10 u + 8 u
= 81 u
= 81 x 45
= 3645
Answer(s): 3645