Question

In the class mean age of 60 % students is 20 yrs. While of the rest is 16 yrs. Find mean age of the whole class.

Answer 1

Explanation:

Total age of 30 boys = 30 x 15 = 450

Total age of the rest of boys after the bot aged 20 years leaves = 450 - 20 = 430

Let x be the age of the younger new comer.

Then,

31

430+x+(x+5)

=15

⇒435+2x=31×15=465

⇒2x=30⇒x=15 years