Multiple choice

Mahanath works twice as fast as Sahay. If Sahay alone can complete a job in 21 days, then in how many days will both of them together finish the same job?

  1. 7 days

  2. 6 days

  3. 5 days

  4. 2 days
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A Correct answer
Explanation

Sahay takes 21 days. Mahanath is twice as fast, so he takes 10.5 days. Combined rate = 1/21 + 1/10.5 = 1/21 + 2/21 = 3/21 = 1/7. Together they take 7 days.

AI explanation

Using the efficiency method, if Sahay takes 21 days, Mahanath works twice as fast and takes 21/2 days. Their combined one-day work is 1/21 + 2/21, which equals 3/21 or 1/7. Therefore, working together they finish the job in 7 days.

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