Question

The number of observations in a group is 40 . if the mean of first 10 is 4.5 and remaining is 3.5 . then find the mean of the whole group?

Answer 1

let the sum of first ten observations be x and other 30 observations be y.
x = 10×4.5
x = 45
y=30×3.5
y=105
mean of all observations = (x+y)÷40
=150/40
=3.75