The average weight of six persons in the lift is 48 kg. If four more persons with average weight 51 kg board the lift, then average weight (in kg) of all the persons in the lift will be
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 49.2
An average cannot be added to another average directly when the groups are of different sizes. Each average is first turned into a total weight (average × number of persons), and the new average is the total of all ten persons divided by 10.
Total weight of the six persons: \(6\times48=288\,\mathrm{kg}\)
Total weight of the four persons: \(4\times51=204\,\mathrm{kg}\)
Average of all ten persons: \(\displaystyle\frac{288+204}{10}=\frac{492}{10}=49.2\,\mathrm{kg}\)