1. Problem Understanding
We want to estimate the number of WhatsApp messages sent per day in India.
This is a product/tech guesstimate — use population → smartphone users → WhatsApp penetration → messages per user → total messages/day.
2. Approach Summary (Top-Down)
Population → smartphone users → WhatsApp users → messages per user per day → total messages/day
3. Step-by-Step Solution
Step 1: Start with India’s population
Use a round figure: 1.4 billion.
Step 2: Estimate number of smartphone users
From our earlier guesstimate: ~550 million smartphone users (blended urban/rural).
Step 3: WhatsApp penetration among smartphone users
WhatsApp is the dominant messaging app in India. Reasonable assumption: ~80–85% of smartphone users actively use WhatsApp.
WhatsApp users ≈ 550M × 0.82 ≈ ~450 million active users
(Use a clean rounded number: ~450M.)
Step 4: Messages per user per day
This varies by user type:
- Heavy users (urban, young): 50–100 messages/day
- Average users: 20–40 messages/day
- Light users (older, rural): 5–15 messages/day
Blend these groups into a conservative average of ~30 messages per user per day.
Rationale: many users forward media and chat in groups; group traffic inflates counts versus 1:1 messages.
Step 5: Total messages per day
Total ≈ 450M users × 30 messages/user/day = ~13.5 billion messages/day
Give a reasonable range to reflect uncertainty in assumptions: ~10–18 billion messages per day.
4. Final Answer
Approximately 10–18 billion WhatsApp messages are sent per day in India, best single-point estimate ≈ 13.5 billion/day.
5. Interviewer-Ready Summary
- Population → 1.4B
- Smartphone users → ~550M
- WhatsApp users → ~450M (≈82% of smartphones)
- Messages/user/day → ~30
- Final: ~13.5B messages/day (range 10–18B)