Correct Option (C)
The problem requires determining the weight of the 5th person by utilizing the provided average weights of different groups. The calculation proceeds as follows:
- The total weight of all 9 persons is computed by multiplying their average weight by the number of persons: 9 persons × 50 kg/person = 450 kg.
- The total weight of the first 5 persons is calculated as: 5 persons × 45 kg/person = 225 kg.
- The total weight of the last 5 persons is calculated as: 5 persons × 55 kg/person = 275 kg.
- When the sum of the weights of the first 5 persons and the last 5 persons is combined (225 kg + 275 kg = 500 kg), the weight of the 5th person is included twice because this individual is part of both groups.
- To isolate the weight of the 5th person, the total weight of all 9 persons is subtracted from this combined sum: 500 kg - 450 kg = 50 kg.
Therefore, the weight of the 5th person is 50 kg.
Incorrect Options:
Options A (45 kg), B (47.5 kg), and D (52.5 kg) are incorrect. These values do not align with the arithmetic derivation based on the given average weights and the principle of accounting for the overlapping individual. Any deviation from 50 kg indicates an error in the calculation or an incorrect application of the concept of averages in overlapping sets.