Multiple choice

A can do a work in 50 days and B in 40 days . They work together for 10 days and then A leaves and B have to finish the work alone. How long will B take to finish it??

  1. 18

  2. 19

  3. 21

  4. 22

  5. 23
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A's rate is 1/50 and B's rate is 1/40. In 10 days, they complete 10*(1/50 + 1/40) = 10*(9/200) = 9/20 of the work. The remaining 11/20 of the work is done by B at a rate of 1/40, taking (11/20) * 40 = 22 days.

AI explanation

Using the least common multiple method, let the total work be 200 units. The daily work rates of A and B are 4 units and 5 units respectively. Working together for 10 days, they complete 90 units, leaving 110 units of work. B must complete the remaining 110 units alone at his rate of 5 units per day, which requires 22 days.

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