Question

The number of boys and girls in a class are in ratio 7:5 the number of boys is 18 more than the number of girls. What is the total class strength?

Answer 1

Given ratio of number of boys to girls is 7:5
Let the number of boys be 7x
and number of girls be 5x
Also given that boys are 18 more than the girls
i.e
7x= 5x+18
7x-5x= 18
2x=18
x=18/2
x=9


Number of boys= 7x= 7*9= 63
Number of girls= 5x= 5*9= 45
Total strength = 63+45
                        = 108 students. 

Answer 2

Boys : girls = 7 : 5
Let the number of boys be 7x
Then the number of girls be 5x

The number of boys is 18 more than the number of girls.
7x = 5x + 18
7x-5x = 18
2x = 18
x = 18/2
x = 9

The number of boys = 7(9) = 63
The number of girls = 5(9) = 45

Total class strength = 63+45
= 108