As per the Manual on Water Supply and Treatment, Ministry of Urban Development, GOI, the fire demand for 1 lakh population is :
- A41,760 L/minCorrect
- B35,050 L/min
- C31,625 L/min
- D21,960 L/min
Solution
Concept
Fire demand formulae
Formula
National Board of Fire Underwriters: Q = 4637 √P (1 − 0.01 √P) L/min (P in thousands)
Step-by-step solution
1. P = 100 (thousands), √P = 10. 2. Q = 4637 × 10 × (1 − 0.1) = 41 733 L/min ≈ 41 760 L/min.
Explanation
Fire demand for large towns is estimated from empirical population-based formulae; for 1 lakh population the National Board of Fire Underwriters formula gives about 41,760 litres per minute.
Why the other options are wrong
Kuichling's formula 3182√P gives about 31,800 L/min, and Freeman's formula gives about 34,000 L/min; these differ from the figure the question seeks.
Shortcut
NBFU: 4637√P(1 − 0.01√P).
Common mistake
Using Kuichling's formula.
Correct answer: A) 41,760 L/min