Question

The average weight of a b and c is 45kg. if the average weight of A and B be 40kg and that of B and C be 43kg then find the weight of B

Answer 1

Let A,B,C represent their respective weights. Then, we have:
$A+B+C=(45\times 3)=135.....\left(i\right)$
$A+B=(40\times 2)=80.....\left(ii\right)$
$B+C=(43\times 2=\mathrm{86.....}(iii)$
Adding (ii) and (iii), we get: A+2B+C =166 .....(iv)
Subtracting (i) from (iv), we get: B=31.
$\therefore$ B's weight =31 kg.