The average age of 10 members of a committee is the same as it was 4 years ago, because an old member has been replaced by a young member.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 ? Choose the most appropriate option.
A) 35	B) 15	C) 40	D) 52	E) 14
C   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.
<result>C</result>
The average age of 10 members of a committee is the same as it was 4 years ago, because an old member has been replaced by a young member.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 ?