Multiple choice

M and N can do a piece of work in 25 days and 30 days respectively. They work together for 5 days and then M leaves the work. N will finish the rest of the work in how many days?

  1. 18 days

  2. 19 days

  3. 20 days

  4. 21 days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

M's rate = 1/25, N's rate = 1/30. Combined rate = 1/25 + 1/30 = 11/150. In 5 days, they complete 5*(11/150) = 11/30 of work. Remaining = 19/30. N alone needs (19/30)/(1/30) = 19 days. The key is finding individual work rates and tracking remaining work.

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