1. **Problem statement:** Calculate the size of the storage cistern needed for 150 students (50 females and 100 males). Each student uses the washroom once a day, and the cistern refills every 1.5 days. 2. **Identify average daily water use per person for washroom use:** - Toilet flushing: 1.6 to 4 gallons per flush - Assume average: $\frac{1.6 + 4}{2} = 2.8$ gallons per flush - Each student uses the washroom once, so 2.8 gallons per person per day 3. **Calculate total daily water use for 150 students:** $$ 150 \times 2.8 = 420 \text{ gallons per day} $$ 4. **Since the cistern is refilled every 1.5 days, total storage needed is:** $$ 420 \times 1.5 = 630 \text{ gallons} $$ 5. **Convert gallons to liters (1 gallon = 3.78541 liters):** $$ 630 \times 3.78541 \approx 2384.7 \text{ liters} $$ **Final answer:** The storage cistern size required is approximately **2385 liters**. This calculation assumes that toilet flushing is the primary washroom water use and one flush per person per day.