Question

The average weight of the group having 3 members is 84. One more person joins the group and now the average becomes 80. Now a fifth person comes whose weight is 3 years more than that of the fourth person replaces the first person. After this, the average weight of the group becomes 79. What is the weight of the first person?

• A. 75
• B. 65
• C. 68
• D. 82
• E. 85

Answer 1

The correct option is A 75

Let the weights of these are A, B, C, D, E
So $A+B+C=84\times 3=252$
And $A+B+C+D=80\times 4=320$
So $D=320-252=68$, so $E=68+3=71$
Now $B+C+D+E=79\times 4=316$
$(A+B+C+D)-(B+C+D+E)=320-316$
So $A-E=4$, so $A=71+4$