Multiple choice

A and B can do a piece of work in 25 days and 30 days respectively. They work together for 5 days and then A leaves. B 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

A's work rate = 1/25 per day, B's = 1/30 per day. Combined rate = 1/25 + 1/30 = 11/150 per day. In 5 days, they complete 5 × 11/150 = 11/30 of work. Remaining = 19/30. B alone does 1/30 per day, so needs 19 days. Option B is correct.

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