Step 1: Calculate total rainfall volume harvested.
Annual rainfall = 400 mm = 0.4 m
Roof area = 500 m\(^2\)
\[
\text{Total volume harvested} = 0.4 \times 500 = 200 \; \text{m}^3
\]
Step 2: Convert to liters.
\[
200 \; \text{m}^3 = 200 \times 1000 = 200{,}000 \; \text{liters}
\]
Step 3: Account for 40% losses.
\[
\text{Effective stored volume} = 200{,}000 \times (1 - 0.40) = 120{,}000 \; \text{liters}
\]
Step 4: Daily water demand.
Population = 3 persons, Demand = 200 lpcd
\[
\text{Daily demand} = 3 \times 200 = 600 \; \text{liters/day}
\]
Step 5: Calculate days of sufficiency.
\[
\text{No. of days} = \frac{120{,}000}{600} = 200 \; \text{days}
\]
Final Answer: \[ \boxed{200 \; \text{days}} \]
Match the various types of impurities present in water in Group I with the appropriate water treatment process given in Group II.
\[\begin{array}{|c|c|} \hline \textbf{Group I} & \textbf{Group II} \\ \hline \text{P: Fine suspended matter} & \text{1: Aeration} \\ \hline \text{Q: Pathogenic bacteria} & \text{2: Plain sedimentation} \\ \hline \text{R: Color, odour and taste} & \text{3: Sedimentation with coagulation} \\ \hline \text{S: Floating matter as leaves} & \text{4: Screening} \\ \hline & \text{5: Disinfection} \\ \hline \end{array}\]
