Question

Find the mean of the following distribution.

$$\begin{array}{cccccc}Class& 100-120& 120-140& 140-160& 160-180& 180-200\\ Frequency& 10& 13& 8& 7& 12\end{array}$$

• A. 149.2
• B. 200
• C. 100
• D. 249.2

Answer 1

The correct option is A 149.2

$$\begin{array}{ccc}\text{Class Mark}& \text{Frequency}& fx\\ \text{110}& \text{10}& \text{1100}\\ \text{130}& \text{13}& \text{1690}\\ \text{150}& \text{8}& \text{1200}\\ \text{170}& \text{7}& \text{1190}\\ \text{190}& \text{12}& \text{2280}\end{array}$$
$N$=50
$\sum fx$ = 7460
Note that $\overline{x}$ = $\frac{\sum fx}{N}$,
where $\overline{x}$ stands for mean and $N$ stands for the sum of frequencies.
$⟹Mean=\frac{7460}{50}=149.2$