The average age of four boys A, B, C and D is 5 years and the average age A, B, D, E is 6 years. C is 8 years old. The age of E is (in years) :

A. 12

B. 13

C. 14

D. 15

Answer: Option A

Solution(By Examveda Team)

According to the question,
$$\eqalign{ & \frac{{A + B + C + D}}{4} = 5 \cr & A + B + C + D = 20.....(i) \cr & \frac{{A + B + D + E}}{4} = 6 \cr & A + B + D + E = 24.....(ii) \cr} $$
If C = 8 years old, put the value of 'C' in equation (i)
∴ A + B + D + 8 = 20
A + B + D = 12.....(iii)
Put the value of equation (iii) in equation (ii)
12 + E = 24
E = 24 - 12
∴ E = 12