Question

A can do a work in 14 days and working together A and B can do the same work in 10 days. In what time can B alone do the work? (i dont get this one, please explain :)

Answer 1

35 days.

Explanation:

A can do the work in 14 days: per day work done by A=1/14

A and B can do the work in 10 days: per day work done by A and B=1/10

Work is done by B per day=1/10–1/14=7/70-5/70=(7–5)/70=2/70=1/35.

So, B takes 35 days.

Answer 2

35 days

Explanation:

A = 14 days

It means per day, work done by A= 1 / 14

A+B = 10 days

Work done by A and B per day = 1 / 10

In what time can B alone do the work?

To solve this, we have

A+B = A alone + B alone

1/10 = 1/14 + B alone

Subtract 1/14 from both sides

1/10 - 1/14 = 1/14 + B alone - 1/14

14-10/140 = B alone

4/140 = B alone

B alone= 1 / 35

Work done of B alone = 1/35

B alone will do the work in 35 days