Kavita can complete a piece of work alone in 12 hours, while Komal can complete the same work alone in 18 hours. Kavita works alone for the first 4 hours and leaves. After that, Komal comes and completes the remaining work by herself. How much time did Komal take to finish the remaining work?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 12 hours
Let's assume that the total work is equal to 1 unit.
Kavita can complete the work alone in 12 hours, so her work rate is 1/12 units per hour.
Komal can complete the work alone in 18 hours, so her work rate is 1/18 units per hour.
Kavita works alone for the first 4 hours and completes a fraction of the work:
Work done by Kavita in 4 hours = (1/12) × 4
= 1/3 units
The remaining work is equal to:
Remaining work = 1 - 1/3
= 2/3 units
Now, Komal completes the remaining work alone. Her work rate is 1/18 units per hour, so the time taken by her to complete the remaining work is:
Time taken by Komal = (2/3) / (1/18)
= (2/3) × (18/1)
= 12 hours