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 45 kg, then the weight of B is:  Answers:
A) 31 kg B) 32 kg C) 33 kg D) 35 kg E) none of these

Rationale: "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 = ( 45 x 2 ) = 90 … . ( iii ) adding ( ii ) and ( iii ) , we get : a + 2 b + c = 170 … . ( iv ) subtracting ( i ) from ( iv ) , we get : b = 35 . b ’ s weight = 35 kg . answer : d"
Answer: D