The Doubling Deal
You won a contest! Pick how to collect your prize over the next 30 days.
Concept
Would you rather have $1,000 today, or a penny that doubles every day for 30 days? Every kid picks the $1,000 — and by day 30 the penny is worth $5.3 million. Kid makes the choice, watches it play out day by day, and discovers why exponential growth is the most counter-intuitive force in math.
The Experience
Kid is offered the choice upfront — $1,000 today, or a penny that doubles daily for 30 days — and almost always picks the $1,000.
A day-by-day tracker shows both options side by side: by Day 10 the penny is only worth $5.12, and the $1,000 still looks like the easy winner.
By Day 20 the penny has quietly grown to $5,242.88 and overtakes the $1,000 without warning — invisible for 20 days, then suddenly ahead.
By Day 30 the penny is worth $5,368,709.12 versus the flat $1,000 — the gut-punch of exponential growth: it looks like nothing until it's everything.
In round two, the kid predicts the crossover day before seeing the data, then verifies it; round three applies the same doubling curve to real-world examples like population growth, viral spread, and compound interest.
What Math Does The Kid Do?
- Doubles a number repeatedly (×2 each step) across 30 steps.
- Tracks and compares two running totals over time.
- Identifies the crossover point where exponential growth overtakes linear.
- Plots both curves and recognizes the "hockey stick" shape.
- Applies the pattern to real-world exponential phenomena.
Why This Matters
You'll walk away understanding exponential growth — the single idea behind compound interest, viral spread, and why small advantages quietly turn into massive ones.
Frequently asked questions
The Doubling Deal is tagged for Grades 3-7.
No — The Doubling Deal plays directly in the browser, right on this page. No login, no download.
Weigh a real decision where the obvious choice isn't always the smart one.
No — The Doubling Deal is free to play, no sign-up needed.