Question

Find the mean of the following data.

$$\begin{array}{cccccc}Class& 0-10& 10-20& 20-30& 30-40& 40-50\\ Frequency& 6& 7& 11& 9& 7\end{array}$$

• A. 72
• B. 30
• C. 18
• D. 36

Answer 1

The correct option is D 36

$$\begin{array}{ccc}\text{Class Mark}& \text{Frequency}& fx\\ \text{15}& \text{6}& \text{90}\\ \text{25}& \text{7}& \text{175}\\ \text{35}& \text{11}& \text{385}\\ \text{45}& \text{9}& \text{405}\\ \text{55}& \text{7}& \text{385}\end{array}$$
$N$=40, $\sum fx$ = 1440,
Note that $\overline{x}$ = $\frac{\sum fx}{N}$,
where $\overline{x}$ stands for mean and $N$ stands for the sum of frequencies.
$⟹Mean=\frac{1440}{40}=36$