An outlet pipe can empty a cistern in 30 minutes. What fraction of the cistern will it empty in 1 minute?
Aptitude
Pipes and Cistern
Difficulty: Easy
Choose an option
Answer
Correct Answer: 1/30
Explanation
Introduction / Context:For constant-rate emptying, the fraction emptied per minute equals the reciprocal of the total emptying time in minutes.
Given Data / Assumptions:
- Full emptying time = 30 minutes.
- Constant rate; the outlet alone is operating.
Concept / Approach:The per-minute emptying fraction is 1/30 of the tank.
Step-by-Step Solution:Total time T = 30 minutes → rate = 1/T = 1/30 tank per minute.In 1 minute, emptied = 1/30 tank.
Verification / Alternative check:30 minutes at 1/30 per minute removes 1 tank total; consistent.
Why Other Options Are Wrong:1/20 and 1/18 are too large; 1/15 halves the time incorrectly.
Common Pitfalls:Switching numerator and denominator when forming the reciprocal.
Final Answer:1/30