Question

If the mean of the following data is 17 then the value of p is

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

Answer 1

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

$\sum f_i$=50
$\sum f_i{x}_i$ = 640+15p
Given mean=17
Mean=$\frac{\sum f_i{x}_i}{\sum f_i}$
17 = $\frac{640+15p}{50}$
Solving, we get p = 14