Selected MCQ

Current Question
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 1
One pipe fills a tank three times as fast as another. Together they fill in 36 minutes. The time taken by the slower pipe is ____.
  • A. 81 min
  • B. 108 min
  • C. 144 min
  • D. 192 min
Correct Answer: C
Explanation:
Let slow rate = x → total = 4x → gives 144 min.
Related Question 2
Pipes P, Q, R fill the tank in 20, 15, 12 minutes. Together fill in ____.
  • A. 5 min
  • B. 10 min
  • C. 15 min
  • D. 20 min
Correct Answer: A
Explanation:
Combined rate.
Related Question 3
Three pipes, A, B, and C, fill the tank in 30, 20, and 15 minutes, respectively. Together they fill in ____.
  • A. 5/11
  • B. 6/11
  • C. 7/11
  • D. 8/11
Correct Answer: B
Explanation:
Combined rate calculation.
Related Question 4
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 5
If two pipes fill a tank in 6 hours, how long does one pipe take if the other fills in 10 hours?
  • A. 5 hours
  • B. 10 hours
  • C. 15 hours
  • D. 20 hours
Correct Answer: C
Explanation:
Using the rate formula gives 15 houRs.