Question

The average age of a group of children increases by
1 year if a 9 year old child joins the group.
The average age of the group decreases by 2 years,
if a 11 year old child leaves the group. Find the
number of children in the group.​

Answer 1

Answer:

5 children

Explanation:

If earlier average of group is x

and

no of children = n, then

nx+9= (n+1)*(x+1) >>(1)

and

nx-11= (n-1)*(x-2) >>(2)

solving it, we get n=5 , x=3