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 :

[A]17 kg

[B]20 kg

[C]26 kg

[D]31 kg

**31 kg**

Weight of B = (A + B)’s weight + (B + C)’s weight – (A + B + C)’s weight

= 40 2 + 43 2 – 45 3

= 80 + 86 – 135 = 31 kg.

Hence option [D] is correct answer.