Question

If A and B together can complete a piece of work in 15 days and B alone in 20 days, then in how many days can A alone complete the work ?
A. 30 days
B. 40 days
C. 45 days
D. 60 days

Answer 1

Answer:

assume B takes x days

to complete the same work,

his rate of work will be 1/x.

both take 15 days to complete the work,

hence the rate of together working is 1/15.

x=60 days. A can do the work in 20 days.

Answer 2

Answer:

A and B complete a work in = 15 days

One day's work of (A + B) = 1/15

B complete the work in = 20 days;

One day's work of B = 1/20

Then, A's one day's work

=1/15−1/20

=4−3/6

=1/60

Thus, A can complete the work in = 60 days.