The average weight of 8 person's increases by 2.5 kg when a new person comes in place of one of them weighing 65 kg. What might be the weight of the new person?

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76Kg

76.5Kg

Data inadequate

85Kg

answer is C.

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Detailed Solution

Given that the average weight of 8 person's increases by 2.5 kg when a new person comes in place of one of them weighing 65 kg

The old average weight of 8 persons is $x$ , so that the total weight is $8 x$

They removed one person of weight $65 k g$ , hence the total weight is $8 x - 65$

A new person entered whoose weight $y$ , then the average weight is $\frac{8 x - 65 + y}{8} = x + 2.5$

cross multiply

$\begin{array}{rcl} 8 x - 65 + y & = & 8 x + 20 \\ y & = & 65 + 20 \\ = & 85 \end{array}$

Therefore, the weight of new person is $85 K g$

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