Question

16. While working 7 hours a day, A

alone can complete a piece of

work in 6 days and B alone in 8

days. In what time would they

complete it together, working 8

hours a day ?

(1) 3 days (2) 4 days

(3) 2.5 days (4) 3.6 days

Answer 1

A can complete the work in 7*6 = 42 hours;

1 hour's work of A = 1/42;

B can complete the work in 7*8 = 56 hours;

1 hour's work of B = 1/56;

(A+B)'s 1 hour's work = 1/42+1/56 = 98/42*56;

(A+B) will take time to complete whole work,

working 7 hours a day = 42*56/98 = 24 hours;

Let X be the no. of days taken, working 8 hours a day to complete the work by A and B together.

Now, using work equivalence method ;

24 = 8*X;

X = 24/8 = 3 days.

So option A 3 days is the right answer.