If P is population of town/city, Q is total quantity of water required during one year for a town/city; what is the formula for maximum daily per capita demand for a town/city ?
- A1·8 × Q / (P × 365)Correct
- B1·8 × Q / (P × 24)
- C1·5 × Q / (P × 365)
- D1·5 × Q / (P × 24)
Solution
Concept
Maximum daily demand
Formula
Max daily demand = 1.8 × average daily demand
Step-by-step solution
1. Average daily per capita demand = Q / (P × 365). 2. Maximum daily demand = 1.8 × average daily demand.
Explanation
The peak factors are 1.8 for the maximum daily demand and 1.5 for the maximum hourly demand (on top of the maximum daily demand).
Why the other options are wrong
1.5 is the factor for maximum hourly demand over the maximum day. Dividing by 24 gives an hourly rate, not a daily rate.
Shortcut
Max day = 1.8 × average day; max hour = 1.5 × average hour of max day.
Common mistake
Using 1.5.
Correct answer: A) 1·8 × Q / (P × 365)