Question

If the mean of the given data is 25, then find the value of p.

$\begin{array}{cc}\text{Class interval}& \text{Frequency}\\ 0-10& 10\\ 10-20& 9\\ 20-30& 8\\ 30-40& p\\ 40-50& 6\end{array}$ [2 MARKS]

Answer 1

Concept: 1 Mark

Application: 1 Mark

$\begin{array}{ccc}\text{Class Mark}& \text{Frequency}& f_i{x}_i\\ \text{5}& \text{10}& \text{50}\\ \text{15}& \text{9}& \text{135}\\ \text{25}& \text{8}& \text{200}\\ \text{35}& \text{p}& \text{35p}\\ \text{45}& \text{6}& \text{270}\end{array}$

$\sum f_i=33+p$

$\sum f_i{x}_i=655+35p$

Mean $=25=\frac{655+35p}{33+p}$

$825+25p=655+35p$

$10p=170$

$p=17$