1. Problem Understanding

We want to estimate the total number of windows (in homes, offices, shops, schools, hospitals, etc.) across Delhi.

This is a logical / abstract guesstimate, where structure matters more than precision.

We’ll use a population → households → buildings → windows per unit approach.

2. Approach Summary (Top-Down)

Population → Households → Windows per Household → Add Commercial + Institutional Buildings → Total Windows

3. Step-by-Step Solution

Step 1: Delhi population

Round number: ~20 million people

Step 2: Estimate number of households

Average household size ≈ 4 people
Households = 20M ÷ 4 = ~5 million households

Step 3: Estimate windows per household

Different home types:

• Slums: ~2 windows
• Small flats: ~4 windows
• Mid-size apartments: ~6 windows
• Large apartments/homes: ~8+ windows

Blend them into a reasonable average:
~5 windows per household

Household windows =
5M × 5 = ~25 million windows

Step 4: Add windows from commercial buildings

Delhi has many:

• Offices
• Markets
• Restaurants
• Shops
• Malls

Assume commercial windows = ~20% of household windows.
(Reasonable: commercial areas are dense but fewer in count.)

Commercial windows =
25M × 20% = ~5 million

Step 5: Add institutional buildings (schools, colleges, hospitals, govt offices)

These buildings are fewer but large.

Assume additional 10% of household windows.

Institutional windows =
25M × 10% = ~2.5 million

Step 6: Total windows in Delhi

• Household windows: 25M
• Commercial: 5M
• Institutional: 2.5M

Total ≈ 32.5 million windows

Round to a clean number:
~30–35 million windows

4. Final Answer

Delhi has around 30–35 million windows.

5. Interviewer-Ready Summary

• Population → 20M
• Households → ~5M
• Avg windows/house → 5
• Household windows → ~25M
• Add commercial (20%) → +5M
• Add institutional (10%) → +2.5M
• Final: ~30–35M windows in Delhi