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 Examveda Team)

According to the question,
Average weight of whole class
= $$\frac{42 × 25 + 28 × 40}{70}$$
= $$\frac{1050 + 1120}{70}$$
= 31 kg