Question

36. The average age of a class of 40 boys was 20 years, the average age of 12 of them was 22 years and that of another 18 was 17 years. Find the average age of the remaining boys? (A) 19 years (B) 21 years (C) 17 years (D) 23 years (E) None of these (Ans : D)

Answer 1

Answer:B)21

Step-by-step explanation:

x-sum of ages of 12 boys

x/12=22

x=264

y-sum of ages of 18

y/18=17

y=306

40-29=11

z-sum of ages of 11 boys

(264+306+z)/40=20

570+z=800

Z=230

230/11=21 yrs