Selected MCQ

Current Question
A pipe fills a cistern in 8 hours and empties in 16 houRs. Net time to fill?
  • A. 8
  • B. 10
  • C. 16
  • D. 24
Correct Answer: C
Explanation:
Net rate = 1/16.
Related Question 1
One tap fills the tank in 2 hours and another empties in 3 houRs. Time to fill tank is ____.
  • A. 5 hours
  • B. 6 hours
  • C. 7 hours
  • D. 8 hours
Correct Answer: B
Explanation:
Net rate = 1/2 − 1/3 = 1/6 → time = 6 hRs.
Related Question 2
A water tank is two-fifths full. Pipe A fills it in 10 minutes, and pipe B empties it. What is the required time?
  • A. 6 min to empty
  • B. 6 min to fill
  • C. 9 min to empty
  • D. 9 min to fill
Correct Answer: A
Explanation:
Net rate depends on the stronger pipe; here, emptying dominates.
Related Question 3
Pipes A, B, C fill tank in 12, 15, 20 houRs. If A alone works, time required is ____.
  • A. 6 hrs
  • B. 6⅔ hrs
  • C. 7 hrs
  • D. 7½ hrs
Correct Answer: C
Explanation:
Based on the given combination.
Related Question 4
Pipes A, B, C fill tank in 12, 15, 20 houRs. Find time together.
  • A. 6 hours
  • B. 6⅔ hours
  • C. 7 hours
  • D. 7½ hours
Correct Answer: C
Explanation:
Combined rate method.
Related Question 5
Three pipes fill a tank in 6 houRs. After 2 hours, one is closed. Remaining time is ____.
  • A. 10
  • B. 12
  • C. 14
  • D. 16
Correct Answer: C
Explanation:
Work-rate adjustment.