The average weight of 7 boys of a group is 54 kg. When a new boy joined the group, the average weight increased by 2 kg. Find the weight of the new boy.​

Correct option is A

Given:

Average weight of 7 boys = 54 kg

When 1 new boy joins, the average becomes 56 kg

Total boys now = 8

Formula Used:

Weight of new boy = New total weight – Original total weight

New total weight = New average × Number of boys after new boy joins

Original total weight = Original average × Number of original boys

Solution:

Original total weight = 54 × 7 = 378 kg

New total weight = 56 × 8 = 448 kg

Weight of new boy = 448 – 378 = 70 kg 

Alternate Solution: ​

Average weight increase when a new person joins = 2 kg 

Total weight increase = 2 $$\times$$ 8 = 16 kg

Weight of new person = 54 + 16 = 70 kg