average Solved Question
(Aptitude discussion)
 The average weight of three men A, B and C is 84 kg. Another man D joins the group and the new average becomes 80 kg if another man E, whose weight is 3kg more than that of D, replace A, then the average weight of B , C, D and E becomes 79 kg. the weight of A is ?

 70 kg
 72 kg
 75 kg
 80 kg
Correct Option: C
From question
A + B + C = 3 x 84 = 252 ....(i)
A + B + C + D = 4 x 80 = 320 ...(ii)
From eq. (ii)  (i)
D = ( 320  252 ) = 68
From question E = D + 3
⇒ E =( 68 + 3 ) = 71
Now , B + C + D + E = 4 x 79 = 316
∴ B + C + D = 316 – 71 = 245
So , A = 320  245 = 75 kg .