The average weight of A, B and C is 45 kg. If the average weight of A and B be 40 kg and that of B and C be 43 kg, then the weight of B is:  Pick
A) 17 kg
B) 20 kg
C) 26 kg
D) 31 kg
E) 32 kg
Explanation:   Let A, B, C represent their respective weights. Then, we have:   A + B + C = (45 x 3) = 135 .... (i)   A + B = (40 x 2) = 80 .... (ii)   B + C = (43 x 2) = 86 ....(iii)   Adding (ii) and (iii), we get: A + 2B + C = 166 .... (iv)   Subtracting (i) from (iv), we get : B = 31.   B's weight = 31 kg.   ANSWER IS 31 kg
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The average weight of A, B and C is 45 kg. If the average weight of A and B be 40 kg and that of B and C be 43 kg, then the weight of B is: