Question

The mean of 100 observations is 50 .if one of the observation which was 50 is replaced by 150 . find the resulting mean.

Answer 1

Given, 
The mean of 100 observations is 50. 
If one of the observations is replaced by 150, 
the resulting mean will be: 
[(100 - 1)*50 + 150)/100] = (4950 +150)/100 
= 51

Answer 2

Mean of 100 observations = 50
Sum of 100 observations = 50 × 100 = 5000
When 50 is replaced by 150, then sum of 100 observations = 5000 – 50 + 150 = 5100

So, mean of the new 100 observations = 5100/100
=>51 answer