Multiple choice

A can finish a work in $18$ days and B can do the same work in $15 $ days. B worked for $10$ days and left the job. In how many days, A alone can finish the remaining work?

  1. $5$ days
  2. $\dfrac{11}{2}$ days
  3. $6$ days
  4. $8$  days
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A's rate is 1/18 work/day and B's rate is 1/15 work/day. B worked for 10 days, completing 10/15 = 2/3 of the work. The remaining 1/3 of the work is completed by A in (1/3) / (1/18) = 6 days.

AI explanation

Assume the total work is the Least Common Multiple of 18 and 15, which is 90 units. The daily work capacities are 5 units for A and 6 units for B. Since B works for 10 days, B completes 60 units, leaving 30 units of work. A works at a rate of 5 units per day, so A requires 30 divided by 5, which is 6 days to finish the remaining work.

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