SSC CGL Pipes and Cisterns Practice Test 7

1. A does a job in 10 days, B in 15 days. Together they finish in:

• A. 5 days
• B. 6 days (Correct)
• C. 7 days
• D. 8 days

Explanation: Combined rate = 1/10+1/15=1/6. Time=6 days.

2. Pipe A fills a tank in 12 hours and Pipe B fills it in 18 hours. Together they fill in:

• A. 6 hours
• B. 7.2 hours (Correct)
• C. 8 hours
• D. 9 hours

Explanation: 1/12+1/18=5/36. Time=36/5=7.2 hours.

3. A can complete a work in 20 days, B can in 30 days. They work together for 6 days. Fraction of work remaining is:

• A. 1/4
• B. 1/3
• C. 2/5
• D. 1/2 (Correct)

Explanation: Together rate = 1/20 + 1/30 = 1/12. In 6 days they complete 6/12 = 1/2, so 1/2 of the work remains.

4. A is twice as efficient as B. B can do a job in 18 days. Together they finish in:

• A. 4 days
• B. 5 days
• C. 6 days (Correct)
• D. 7 days

Explanation: A does in 9 days. Together: 1/9+1/18=3/18=1/6. Time=6 days.

5. Pipe A fills in 6 hours, Pipe B fills in 8 hours, Pipe C empties in 12 hours. All open together, tank fills in:

• A. 4.8 hours (Correct)
• B. 5 hours
• C. 5.6 hours
• D. 6 hours

Explanation: Rate=1/6+1/8−1/12=4/24+3/24−2/24=5/24. Time=24/5=4.8 hours.

6. 6 men can do a job in 12 days. How many men to do same job in 8 days?

• A. 7
• B. 8
• C. 9 (Correct)
• D. 10

Explanation: 6×12=8×x → x=9 men.

7. A does 1/5 of work in 4 days. B does rest in 12 days. Both work alternately starting with A. Job completes in:

• A. 16 days
• B. 17 days (Correct)
• C. 18 days
• D. 20 days

Explanation: A's rate=1/20 per day, B's rate=4/5÷12=1/15. In 2-day cycle: 1/20+1/15=7/60. After 16 days (8 cycles)=56/60. Remaining=4/60=1/15. A works day 17 finishing 1/20 only, so B finishes. Total≈17 days.

8. A pipe leaks. It can fill tank in 10 hours but due to leak, takes 12 hours. Leak will empty full tank in:

• A. 50 hours
• B. 55 hours
• C. 60 hours (Correct)
• D. 65 hours

Explanation: Fill rate=1/10, effective=1/12. Leak=1/10−1/12=1/60. Empties in 60 hours.

9. A, B, C together do a job in 4 days. A and B together in 6 days, B and C together in 8 days. A alone does in:

• A. 8 days (Correct)
• B. 9 days
• C. 10 days
• D. 12 days

Explanation: 1/A+1/B+1/C=1/4. 1/A+1/B=1/6. 1/B+1/C=1/8. Subtracting: 1/A−1/C=1/6−1/8=1/24. Also 1/C=1/4−1/6=1/12. So 1/A=1/24+1/12=3/24=1/8. A=8 days.

10. If 15 workers take 6 days for a job, 9 workers take:

• A. 8 days
• B. 9 days
• C. 10 days (Correct)
• D. 12 days

Explanation: 15×6=9×d → d=10 days.

11. A does 40% of work in 8 days. He then calls B, and together they finish remaining 60% in 6 days. B alone would do full job in:

• A. 15 days
• B. 20 days (Correct)
• C. 25 days
• D. 30 days

Explanation: A's rate=40%/8=5% per day. Together=60%/6=10% per day. B=5% per day. B alone=100%/5=20 days.

12. A cistern has two inlets that fill it in 10 and 12 hours. Time to fill together:

• A. 5.45 hours (Correct)
• B. 6 hours
• C. 6.36 hours
• D. 7 hours

Explanation: 1/10+1/12=11/60. Time=60/11≈5.45 hours.

13. A, B together finish work in 18 days. B, C in 24 days. A, C in 36 days. Time for A alone:

• A. 36 days
• B. 48 days (Correct)
• C. 54 days
• D. 72 days

Explanation: 2(1/A+1/B+1/C)=1/18+1/24+1/36=4/72+3/72+2/72=9/72=1/8. So 1/A+1/B+1/C=1/16. 1/A=1/16−1/24=3/48−2/48=1/48. A=48 days.

14. 8 men complete 1/4 of a task in 10 days. More men needed to complete remaining 3/4 in 15 days:

• A. 6
• B. 8 (Correct)
• C. 10
• D. 12

Explanation: 8 men×10 days=80 man-days for 1/4. Full job=320 man-days. Remaining=240 man-days in 15 days → 16 men. Additional=16−8=8.

15. A tap fills a tank in 5 hours and empties it in 15 hours. Net fill time when both open:

• A. 6.25 hours
• B. 7.5 hours (Correct)
• C. 8 hours
• D. 9 hours

Explanation: Net=1/5−1/15=2/15. Time=15/2=7.5 hours.