The average age of 120 students in a group is 13.56 years. 35% of the number of students are girls and the rest are boys. If the ratio of the average age of boys and girls is 6 : 5, then what is the average age (in years) of the girls?

A. 14.4

B. 10

C. 11.6

D. 12

Answer: Option D

Solution (By Examveda Team)

7 × 5a + 13 × 6a = 20 × 13.56
35a + 78a = 271.2
113a = 271.2
a = 2.4
Average of girls = 5a
= 5 × 2.4
= 12