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

1) 8
2) 6
3) 5
4) 7

• 5 children
  
  If earlier average of group is x
  and
  no of children is n, then
  nx+9= (n+1)*(x+1)
  and
  nx-11= (n-1)*(x-2)
  
  solving it, we get n=5 , x=3
• 12 years agoHelpfull: Yes(0) No(0)
• 5 childern of avg. age 3
• 12 years agoHelpfull: Yes(0) No(0)