The average weight of P, Q and R is 47 kg. If the average weight of P and Q be 32.5 kg and that of Q and R be 48.5 kg, then what is the weight of Q (in kgs)?
$$\frac{P+Q+R}{3}=47 \rightarrow P+Q+R = 47\times 3 = 141$$ -------(1)
$$\frac{P+Q}{2}=32.5\rightarrow P+Q = 32.5\times 2 = 65$$ -------(3)
$$\frac{Q+R}{2}=48.5\rightarrow Q+R = 48.5\times 2 = 97$$ -------(3)
(2)+(3)-(1)$$\Rightarrow P+Q+Q+R-P-Q-R = 65+97-141=21$$
$$\Rightarrow Q = 21$$
So the answer is option B.
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