Question

the mean of 20 no.s is 18 . if 2 is added to each no , what is the new mean ?

Answer 1

It's 20 ......bcoz means also increases by the same no. If all observations are increased by that no.

Answer 2

mean of observation is equals to 18
sum of observation is equals to mean × number of observation
I 8×20 =360
when 2 is added to each number
new sum = 360 + 2×20
= 400
new mean = new sum /no. of observation
=400/20
=20
new mean is 20