# If the mean of frequency distribution is 8.1

Question:

If the mean of frequency distribution is $8.1$ and $\Sigma f_{i} x_{i}=132+5 k, \Sigma f_{i}=20$, then $k=$

(a) 3
(b) 4
(c) 5
(d) 6

Solution:

Given:

$\sum f_{i} x_{i}=132+5 k, \Sigma f_{i}=20$ and mean $=8.1$

Then,

Mean $=\frac{\sum f_{i} x_{i}}{\sum f_{i}}$

$8.1=\frac{132+5 k}{20}$

$162=132+5 k$

$5 k=30$

$k=6$

Hence, the correct option is (d).