Question

A can do a piece of a work in 7 days, A and B can do the work together in 6 days. If B alone does the work how many days does he require?

• A. 40
• B. 42
• C. 43
• D. 45

Answer 1

The correct option is B

42

Let the time taken by B be ‘x’

A can do the work in 7 days.

Hence the work done by A in one day = $\frac{1}{7}$

A and B can together finish the work in 6 days

Hence the work done by A and B in one day = $\frac{1}{6}$

$\therefore$ work done by B in one day = Work done by A and B in one day - work done by A in one day

= $\frac{1}{6}$ - $\frac{1}{7}$

= $\frac{7-6}{42}$

= $\frac{1}{42}$

Since Work done by B in one day is $\frac{1}{42}$ , B alone can complete the work in 42 days