The average marks (out of 100) of boys and girls in an examination are 75 and 80, respectively. If the average marks of all the students in that examination are 78. Find the ratio of the number of boys to the number of girls.

Correct option is A

Given:

Average marks of boys = 75

Average of girls = 80

Total average of both boys and girls = 78

Solution:

To find the ratio we use alligation rule:

Alligation rule:

Clearly the ratio of number of boys to number of girls = 2:3