## The average weight of a group of boys is 30 kg. After a boy of weight 35 kg joins the group, the average weight of the group goes up by 1 kg. Find the number of boys in the group originally?

A. 4

B. 6

C. 7

D. 9

### Answer

Correct Answer: **A. 4 **

### Solution

Let the number of boys in the group originally be x.

Total weight of the boys = 30x

After the boy weighing 35 kg joins the group, total weight of boys = 30x + 35

So 30x + 35 + 31(x + 1) = > x = 4.