Interview Questions › Guesstimate

Estimate number of plastic bottles used daily in a metro city

Estimate the number of single-use and packaged plastic bottles (water, soft drinks, juices, personal care) consumed and discarded daily in a metro city of 10 million people.

Context

Consider packaged drinking water, carbonated soft drinks, dairy beverages, and personal/home cleaning products.

Clarifying questions to ask first

• Are we focusing strictly on single-use beverage bottles or including shampoo/detergent bottles? (All plastic bottles)
• Does this include bottles recycled and discarded? (All consumed bottles).

How to approach it

1. Segment by Product Category: Packaged Drinking Water, Carbonated Beverages, Juices/Energy Drinks, Household/Personal Care
2. Segment population into Income Tiers & Daily Mobility (Commuters/Office Workers vs Home/Residential)
3. Calculate bottles per capita per day across categories
4. Formulate waste management and recycling implications

Framework: Total Daily Bottles = (Packaged Water Bottles) + (Soda & Beverage Bottles) + (Household/Personal Care Dailyized)

Sample answer

• Packaged Drinking Water (0.5L / 1L): 10M pop × 0.35 bottles/day = 3.5 Million bottles
• Carbonated Soft Drinks & Juices: 10M pop × 0.15 bottles/day = 1.5 Million bottles
• Household & Personal Care (shampoo, soap, cleaners annualized): ~0.2 Million bottles/day

1. Total daily bottles consumed = 3.5M (water) + 1.5M (beverages) + 0.2M (homecare) = ~5.2 Million plastic bottles/day
2. Per capita average = ~0.52 plastic bottles per citizen per day

Executive estimate: ~5.0 to 5.5 Million plastic bottles used daily in a 10M metro (~70% packaged water, ~30% soft drinks/juices); generating ~100 tons of plastic waste daily.

What interviewers look for

• Category Decomposition (Water vs Soda vs Homecare)
• Per Capita Consumption Modeling
• Commuter & Commercial Impact
• Environmental Sanity Check