Curated essays & number phenomena
NumberChan Reads
Fascinating math, counterintuitive probabilities, and real-world number dynamics — each paired with a NumberChan tool so you can try the idea yourself.
- 01 · Data patterns2 min read
Benford’s Law: Why So Many Real Numbers Start With 1
In many real-world datasets, about 30% of numbers begin with the digit 1 — and forensic accountants use that to spot figures worth a second look.
Read article - 02 · Mental math2 min read
The Rule of 72: Doubling Your Money in Your Head
Divide 72 by an annual growth rate and you get a surprisingly close estimate of how many years it takes to double — a trick printed in 1494.
Read article - 03 · Behavioral pricing2 min read
Why $19.99 Still Feels Cheaper Than $20: The Left-Digit Effect
A one-cent difference can shift how expensive something feels, because our brains anchor on the first digit we read.
Read article - 04 · Probability2 min read
The Birthday Paradox: Why 23 People Is Enough
With just 23 people in a room, the chance that two share a birthday is slightly better than a coin flip. The trick is counting pairs, not people.
Read article - 05 · Economics2 min read
The Cantillon Effect: Why Inflation Doesn’t Reach Everyone at Once
An 18th-century banker argued that new money changes prices unevenly as it travels — so who receives it first matters.
Read article - 06 · Probability2 min read
The Monty Hall Problem: Why You Should Switch Doors
Three doors, one car, two goats. After the host reveals a goat, switching wins two times out of three — an answer that famously angered thousands of readers.
Read article - 07 · Loans2 min read
Amortization Shock: Where Your Early Mortgage Payments Go
On a 30-year mortgage, most of each early payment covers interest. Here is the math on a $300,000 loan — and what changes it.
Read article - 08 · Online audiences1 min read
The 1% Rule of the Internet and the Math of Creator Income
Most people online watch, a few react, and very few create. That lopsided pattern shapes how views, engagement, and creator earnings add up.
Read article - 09 · Business math1 min read
Margin vs. Markup: The Costly Mix-Up in Pricing
A 50% markup is only a 33.3% profit margin. Confusing the two can quietly erase the profit you planned for.
Read article - 10 · Decision theory2 min read
The St. Petersburg Paradox: When Infinite Value Isn’t Worth Much
A simple coin game has an infinite expected payout, yet almost nobody would pay much to play. The puzzle helped invent the idea of utility.
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