Question

The average of 35 observations is 20, out of which mean of first 18 observations is 15 and mean of last 18 observations is 25. find the 18 observations

Answer 1

Let x is the total sum of observations.
then x/35=20
x=700
and let sum of 1st 18th observation be a and sum of last 18th observation be b.
then a=270 and b =450
as 18th observation is taken twice.
18th obs= a+b-x
=20.

hope it may helps you....