<PRE><B>Question 983309</B>
The Average age of family is 50, a new baby was born then one grandpa was died at the age of 65,what is average age of family present now?
:
Effectively 65 is subtracted from the total of their ages, but the number of family members remain the same, but you have to know how many in the family
let n = no. of family members
then
50n = total of all family ages
:
then when grandpa was alive
{{{(50n)/n = 50}}}
when grandpa is replaced by a baby (age 0)
{{{(50n-65)/n}}} is the new average
:
:
we can demonstrate this, suppose their are 10 family members, then sum will be
50 * 10 = 500, an average of 50
When Grandpa is replace by a baby
(500-65)/10 = 43.5 is the average now
What if their were 20 family member then
50 * 20 = 1000
When Grandpa is replaced by a baby
1000-65/20 = 46.75 is the average now</PRE>