The number of student in class IX and class X is 42 and 45, respectively. The ratio of the number of boys to girls in classes is IX and X is 9 : 5 and 8 : 7, respectively, What is the difference between the total number of boys and the total number of girls in both the classes taken together?

Options
a) 11
b) 12
c) 17
d) 15

Solutions

As per questions
Total student class ix = 42
Total student class x = 45
Class ix boys and girls ratio = 9 : 5
Class x boys and girls ratio = 8 : 7

Class ix No. of boys =
= 27
No. of girls =
= 15
Class x No. of boys =
= 24
No. of girls =
= 15

Total No. of boys both classes = 27 + 27 = 51
Total No. of girls both classes = 15 + 21 = 36
Difference = 51 – 36 = 15

Ans: d) 15