The average weight of 3 packets A, B and C is 84 kg. Another packet D added into the group and the average now becomes 80 kg. If another packet E, whose weight is 3 kg more than that of D, replaces A then the average weight of B, C, D and E becomes 79 kg. The weight of A is:	Choose the correct choice from the following: A) 70 kg B) 72 kg C) 75 kg D) 80 kg E) none of these

Rationale: explanation : a + b + c = ( 84 x 3 ) = 252 kg , a + b + c + d = ( 80 x 4 ) = 320 kg . d = ( 320 - 252 ) = 68 , e = ( 68 + 3 ) = 7 l . b + c + d + e = ( 79 x 4 ) = 316 . ( a + b + c + d ) - ( b + c + d + e ) = ( 320 - 316 ) kg = 4 kg . a - e = 4 = a = ( 4 + e ) = 75 kg answer : c
Answer: C