Question

The mean of first 5 observations is 20 and the mean of last 5
observations is 45. What is mean of all 10 observations?​

Answer 1

Mean = sum of all the observations/number of observations.

So,
First five observations
20 x 5 = 100.

Last five observations.

45 x 5 = 225.

All the ten observations.

100 + 225 = 325.

325/10 = 32.5 is the mean of all the ten observations