A can do a piece of work in 15 days and B in 20 days. They began the work together but A left after 4 days. In how many days will B complete the remaining work? MCQ with Answer and Explanation

A can do a piece of work in 15 days and B in 20 days. They began the work together but A left after 4 days. In how many days will B complete the remaining work?
A. 10(1/3) days
B. 10(2/3) days
C. 9(1/3) days
D. 8 days
Answer: Option B
Solution (By JKSSB Mock Tests)
Total work = LCM(15, 20) = 60 units. Efficiency of A = 4, B = 3. Combined efficiency = 7. In 4 days, work completed = 4 * 7 = 28 units. Remaining work = 60 - 28 = 32 units. Time taken by B to complete remaining work = 32 / 3 = 10(2/3) days.

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Practice More Time and Work Questions

Question #1
A can complete a work in 13 days and B in 26 days. After working together for 5 days, what percentage of work remains?
A. 44.81
B. 42.31
C. 49.81
D. 47.31

Correct Answer: Option B


Explanation:
Remaining work = (1 - 5*(1/13+1/26))×100 = 42.31%.

This question belongs to: Maths Time and Work
Question #2
A can complete a work in 17 days and B can complete the same work in 32 days. If they work together, in how many days will the work be completed?
A. 13.1
B. 11.1
C. 15.1
D. 17.1

Correct Answer: Option B


Explanation:
Combined rate = 1/17 + 1/32. Time = 1 ÷ combined rate = 11.1 days.

This question belongs to: Maths Time and Work
Question #3
Three pumps working 8 hours a day can empty a tank in 2 days. How many hours a day must 4 pumps work to empty the same tank in 1 day?
A. 16 hours
B. 15 hours
C. 12 hours
D. 10 hours

Correct Answer: Option C


Explanation:
Using P1 * D1 * H1 = P2 * D2 * H2: 3 * 2 * 8 = 4 * 1 * H2 => 48 = 4 * H2 => H2 = 12 hours.

This question belongs to: Maths Time and Work