The average weight of $8 boys is 57 Kg,$ if weight of $7 of them are 64, 42, 29, 39, 80,$ 52 and 55 kg, then the weight of the 8th student is

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answer is B.

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Detailed Solution

Concept-To determine the combined weight of the eight lads, we shall apply the average calculation. The weights of the seven lads will be added up. The weight of the eighth kid will be determined by subtracting the weights of the previous seven boys from the total weight. To determine the weight of the eighth boy., we shall deduct the first two amounts.
formulas employed
The following is the formula for n's mean weight:
Average Weight = Sum of N Individual Weights.
Eight boys weigh an average of 57 kg, as far as we are aware. In the formula for the average weight, we will change n to 8 and average weight to 57:
8 persons weigh a total of 57 pounds.
By dividing 8 by 57, we have 57/8, which is the combined weight of 8 people.
8 people weigh a total of 456 pounds.
The total weight of 8 people, according to our calculations, is 456 kg. We are aware of the weights of 7 of the eight individuals. We'll go ahead and suppose that the eighth boy weighs x kg. Thus, the eight persons will weigh a total of