Tag: mental-math
Concepts
- Anchor Numbers Worth Memorising
- The Quick At-the-Money Option Price Formula
- The Card-Pack Trading Game
- Comparing Huge Powers Without a Calculator
- Compounding Shortcuts for Repeated Growth
- Dice-Based Trading Games
- Units and Dimensional Analysis
- Divisibility Tests and Digit Sums
- Estimating Square Roots
- Approximating Exponential Growth
- Fast Division and Reciprocals
- Fermi Estimation
- Financial Anchor Numbers Worth Memorising
- First-Order Approximations in Your Head
- Converting Fractions, Decimals and Percentages
- GCD and LCM Puzzles
- Finding the Last Digit of a Huge Power
- Estimating Logs and Powers of Two
- Market-Sizing Questions
- Doing Arithmetic Fast Under Pressure
- Modular Arithmetic in Puzzles
- Multiplying Numbers Near a Round Base
- Converting Odds and Probabilities Quickly
- Orders of Magnitude and Rounding Discipline
- Percentage Changes and Reversing Them
- Estimating Physical Quantities From Scale
- Square-Root-of-Time Scaling in Your Head
- The Rule of 72
- Squaring Numbers in Your Head
- Summing an Infinite Series in Your Head
- Counting Trailing Zeros in a Factorial
- Weighted Averages and Mixture Shortcuts
Interview Questions
- 999 times 999 in your head
- The angle between the hands at 7:20
- How many breaths in a lifetime?
- One hundred days after a Monday
- Adding 1 to 100 the way Gauss did
- How many times does a heart beat in a lifetime?
- How many seconds are in a year?
- The square root of 12345678987654321
- Squaring a number that ends in 5, instantly
- Add up every date in a 31-day month
- 12345679 times 9, and its friends
- Two to the hundred against ten to the thirty