UPSC CDS 2 2020 Math Paper

We have the 7 family members are 2,5,12,18,38,40 and 60 years respectively.
So, mean =

2+5+12+18+38+40+60

7

= 25
After 5 years a new member x age is added. and mean is increase 1.5 years.
So, now mean = 26.5 years
⇒

7+10+17+23+43+45+65+x

8

=26.5
⇒ 210+x=212
⇒ x=2