### 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

### Solution(By Apex Team)

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

A. 20
B. 21
C. 28
D. 32

A. 18
B. 20
C. 24
D. 30

A. 10 years
B. 10.5 years
C. 11 years
D. 12 years