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