The average weight of A, B and C is 60 kg. If the average weight of A and B be 70 kg and that of B and C be 50 kg, then the weight of B is:
Choose one:
A) 50 kg  B) 60 kg  C) 55 kg  D) 57 kg  E) 62 kg

Rationale: "explanation let a , b , c represent their respective weights . then , we have : a + b + c = ( 60 x 3 ) = 180 â € ¦ . ( i ) a + b = ( 70 x 2 ) = 140 â € ¦ . ( ii ) b + c = ( 50 x 2 ) = 100 â € ¦ . ( iii ) adding ( ii ) and ( iii ) , we get : a + 2 b + c = 240 â € ¦ . ( iv ) subtracting ( i ) from ( iv ) , we get : b = 60 . b â € ™ s weight = 60 kg . answer b"
Answer: B