# The mean of 100 observations is 50.

Question:

The mean of 100 observations is 50. If one of the observations 50 is replaced by 150, the resulting mean will be
(a) 50.5
(b) 51
(c) 51.5
(d) 52

Solution:

(b) 51

Mean of 100 observations = 50

Sum of 100 observations $=100 \times 50=5000$

It is given that one of the observations, 50, is replaced by 150.
∴ New sum = (5000 -">- 50 + 150) = 5100
And,

Resulting mean $=\frac{5100}{100}=51$