If A can complete a task in 10 days and B in 15 days, how long will they take working together?
Correct answer: B. 6 days
- A. 5 days
- B. 6 days
- C. 12.5 days
- D. 25 days
Explanation
In one day A does one tenth and B one fifteenth, and the sum is one sixth, so together they finish in 6 days. The joint time is always shorter than either individual time, which rules out the last two options at once. Adding rates rather than times is the key step.
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