Question

A works twice as fast as B. If B can complete a piece of work independently in 12 days, then what will be the number of days taken by A and B together to finish the work?

• A. 4
• B. 6
• C. 8
• D. 18

Hint:

If A is k times as efficient as B, A's time = B's time / k.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Work efficiency is inversely proportional to time.

Step 2: Detailed Explanation:
B takes 12 days, so B's one day work = \(\frac{1}{12}\).
A is twice as fast, so A's one day work = \(\frac{2}{12} = \frac{1}{6}\).
Combined one day work = \(\frac{1}{12} + \frac{1}{6} = \frac{1}{12} + \frac{2}{12} = \frac{3}{12} = \frac{1}{4}\).
Thus time taken together = 4 days.

Step 3: Final Answer:
A and B together will finish in 4 days.