Question

The mean of $4$ observations is $16$, including one new observation, the mean is $20$. Find the newly included observation.

• A. 100
• B. 60
• C. 70
• D. 36

Answer 1

Answer: (D)

36

$4$ observations be $S$
Then mean $=16$
$16=\frac{s}{4}$
$s=16\times 4=64$
Lets find the newly included observation be $X$ then the sum of the observations be $5$,
Mean $=$ $\frac{S+X}{5}$

$20=\frac{64+X}{5}$
$64+X=20\times 5$
$X=100-64$
$X=36$
So, the newly included observation be $36$.