## Aptitude question and answer on Average

Question : The average weight of 3men A,B and C is 84 kg.Another man D joins the group and the average now becomes 80 kg. If another man 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
A.    70 kg
B.    72 kg
C.    75 kg
D.    80 kg

Explanation:
A+B+C=(84 x 3) = 252 kg,

A+B+C+D=(80 x 4)= 320 kg.

$\dot{..}$ D=(320-252) kg = 68 kg,

E= (68+3) kg = 71 kg.

B+C+D+E = (79 x 4) = 316 kg.

Now  (A+B+C+D)-(B+C+D+E) =(320-316) kg=4 kg.

$\dot{..}$  A-E = 4
=> A =(4+E) = 75 kg.