Work & Time:

1. Q: A can do a job in 10 days. How much work does A do in 1 day?
   Answer: 1/10 

2. Q: B can do a job in 5 days. How much work does B do in 2 days?
   Answer: 2/5

3. Q: A can complete a task in 8 days. How much of the work is done in 3 days?
   Answer: 3/8

4. Q: A can do a job in 6 days. B can do the same job in 12 days. Working together, how long will they take?
   Answer: 1/6+1/12=1/4 → 4 days

5. Q: A and B together can do a job in 5 days. If A alone can do it in 10 days, how long will B take alone?
   Answer: 1/5-1/10=1/10 → 10 days

6. Q: A can do a job in 15 days, B in 20 days. Working together, how long will they take?
   Answer: 1/15+1/20=7/60 → 60/7≈8.57 days 

7. Q: A can do a job in 12 days. B can do it in 18 days. They work together for 4 days. What fraction is left?
   Answer: Work done = 4\times (1/12+1/18)=4\times 5/36=20/36=5/9 → Remaining = 4/9

8. Q: A can do a job in 10 days. B can do it in 15 days. A works for 3 days, then B finishes it. Total time?
   Answer: A does 3/10, remaining 7/10. B takes (7/10)\times 15=10.5 days → Total = 13.5 days

9. Q: A and B can do a job in 6 days. B and C in 8 days. A and C in 12 days. Find A, B, C’s individual work rates.
   Answer: Use system of equations. A = 1/8, B = 1/24, C = 1/12

10. Q: A can do a job in 5 days. B is 50% more efficient. How long will B take?
    Answer: A’s rate = 1/5 → B’s rate = 1.5 × 1/5 = 3/10 → Time = 1÷(3/10)=10/3=3.33 days

11. Q: A and B can do a job in 10 days. B and C in 15 days. A and C in 12 days. Find time taken by A, B, C together.
    Answer: Add all: 1/10+1/15+1/12=(6+4+5)/60=15/60=1/4 → Together = 4 days 

12. Q: A can do a job in 18 days. B in 12 days. C in 6 days. All start together. C leaves after 2 days. Total time?
    Answer: Work in 2 days = 2×(1/18+1/12+1/6)=2×(1/2)=1 → Done!

13. Q: A can do a job in 20 days. B in 30 days. They work alternately starting with A. How long to finish?
    Answer: A + B in 2 days = 1/20+1/30=1/12 → 12 days for full work → 24 days

14. Q: A can do a job in 10 days. B in 15 days. C in 30 days. All work together. How long will they take?
    Answer: 1/10+1/15+1/30=1/5 → 5 days

15. Q: A can do a job in 6 days. B in 8 days. C in 12 days. A works for 2 days, then B and C finish. Total time?
    Answer: A does 2/6=1/3, remaining = 2/3. B + C = 1/8+1/12=5/24 → Time = (2/3)÷(5/24)=3.2 days → Total = 5.2 days

16. Q: A is twice as efficient as B. Together they do a job in 12 days. How long will B take alone?
    Answer: Let B = x → A = 2x → x+2x=3x=1/12 → x = 1/36 → B = 36 days 

17. Q: A and B can do a job in 16 days. A alone in 24 days. How long will B take alone?
    Answer: 1/16-1/24=1/48 → B = 48 days

18. Q: A and B can do a job in 10 days. A alone in 15 days. After 5 days, A leaves. B finishes the rest. Time?
    Answer: A + B in 5 days = 5×(1/10)=1/2 → Remaining = 1/2. B’s rate = 1/10-1/15=1/30 → Time = 1/2÷1/30=15 days → Total = 20 days

19. Q: A can do a job in 9 days. B in 12 days. C in 18 days. All work together. How long to complete the job?
    Answer: 1/9+1/12+1/18=13/36 → Time = 36/13≈2.77 days

20. Q: A, B, and C can do a job in 4, 6, and 12 days respectively. How long will they take together?
    Answer: 1/4+1/6+1/12=1 → 1 day