An outlet pipe can empty a cistern in 30 minutes. What fraction of the cistern will it empty in 1 minute?

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