Question

A and B together can complete a work in 12 days A alone can complete it in 20 days If B now does the work for half a day dally Then in how many days A and B together will complete the work?

• A. 15 days
• B. 20 days
• C. 45 days
• D. 30 days

Answer 1

Answer: (A)

15 days

B's 1 day's work $=\frac{1}{12}-\frac{1}{20}=\frac{2}{60}=\frac{1}{30}$
(A + B)'s 1 day's work $=\frac{1}{20}+\frac{1}{60}=\frac{4}{60}=\frac{1}{15}$.[B works for half day only]
So, A and B together will complete the work in 15 days.