Question

If the mean of the following data is 20 then the value of p is ___

$$\begin{array}{cccccc}{x}_i& \text{10}& \text{p}& \text{18}& \text{21}& \text{25}\\ f_i& \text{10}& \text{15}& \text{7}& \text{9}& \text{9}\end{array}$$

• A. 24
• B. 13
• C. 12
• D. 11

Answer 1

The correct option is A

24

$$\begin{array}{ccc}{x}_i& f_i& f_i{x}_i\\ \text{10}& \text{10}& \text{100}\\ \text{p}& \text{15}& \text{15p}\\ \text{18}& \text{7}& \text{126}\\ \text{21}& \text{9}& \text{189}\\ \text{25}& \text{9}& \text{225}\end{array}$$

$\sum f_i$=50
$\sum f_i{x}_i$ = 640+15p
Given mean=20
$20$ = $\frac{640+15p}{50}$

$20\times 50$ = $640+15p$

$1000$ = $640+15p$

$15p$ = $360$

$p$ = $\frac{360}{15}$

$p$ = $24$