Question

A and B together can complete a work in 12 days. A alone can complete it in 20 days. If B does the work only for half a day daily, then in how many days A and B together will complete the work?

• A. 10 days
• B. 11 days
• C. 15 days
• D. 20 days

Answer 1

The correct option is C

15 days

B’s 1 day’s work = $(\frac{1}{12}-\frac{1}{20})=\frac{2}{60}=\frac{1}{30}$

B's half day work = $\frac{1}{30\times 2}$ = $\frac{1}{60}$

Now, (A+B)’s 1 day’s work = $(\frac{1}{20}+\frac{1}{60})=\frac{4}{60}=\frac{1}{15}[\because$ B works for half day only]

So, A and B together will complete the work in 15 days.