There are two groups A and B of a class, consisting of 42 and 28 students respectively. If the average weight of group A is 25 kg and that of group B is 40 kg, find the average weight of the whole class.

A. 69 kg B. 31 kg C. 70 kg D. 30 kg Answer: Option B
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Solution(By Apex Team)

According to the question, Average weight of whole class $\begin{array}{l}=\large\frac{42\times25+28\times40}{70}\\ =\large\frac{1050+1120}{70}\\ =31\mathrm{~kg}\end{array}$

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