Multiple choice

A and B together can do a piece of work in $ 6\dfrac{2}{3} $ days , but B alone can do it in $10$ days. How long will A take to do it alone ?

  1. $12$ days
  2. $20$ days
  3. $25$ days
  4. $28$ days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The combined rate of A and B is 1/(20/3) = 3/20 work per day. Since B's rate is 1/10 work per day, A's rate is 3/20 - 1/10 = 3/20 - 2/20 = 1/20 work per day. Thus, A takes 20 days to complete the work alone.

AI explanation

Using the formula for work rates, 1/A plus 1/B equals 3/20 and 1/B equals 1/10. Substituting the second equation into the first gives 1/A equals 3/20 minus 1/10, which equals 1/20. Therefore, A alone would take 20 days to complete the work.

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