Question

The average age of 10 members of a committee is the same as it was 4 years ago, because an old member has been replaced by a young member.

Find how much younger is the new member ?

Answer 1

Let the sum of nine member (total) =x
and the age of old one=z
so its average 4 yrs before=(x+z)/10.
after 4 yrs let z be replaced by y.
so now avg=(x+4*10+y)/10

now (x+z)/10=(x+40+y)/10
so after solving it found
z=y+40.
so old person is 40yrs older than young one.

Answer 2

Answer:

40 years

Step-by-step explanation:

Let the members be Old Having age O + other 9 having ages x and New one having age Y

Sum of their ages = (Y + 9 × x) and average = (Y + 9 × x)/10

Before 4 years sum was (O + 9 x – 10 × 4) and average = (O + 9 x – 10 × 4) /10

equating, Y + 9 x = O + 9x – 40

Y = O – 40

Younger is 40 years younger than Old one.