Interactive lessons
A calculator gives you the answer. These lessons show you why — with animated simulators and experiences where you drag, guess and watch it happen. The concept in practice, not just the number.
The 8th wonder of the world
Guess what $200/month becomes in 30 years, watch the snowball grow in an animated chart, and see the cost of waiting.
Where your loan payment goes
See what a $300k mortgage really costs, compare both amortization systems, and why your first payment is almost all interest.
Why diets stall
Only 7% of your burn comes from the gym. See your metabolism from the inside and why the scale slows down.
The debt that never ends
Paying every month while the balance stays put isn't your imagination. Find the invisible line between paying and progressing.
The average lies
A billionaire walks into a bar and everyone becomes a millionaire — on average. See how one outlier wrecks a statistic.
The percentage trap
Up 50% then down 50% doesn't bring you back. Learn why percentages neither add up nor cancel out.
The birthday paradox
In a room of 23 people, the odds two share a birthday are 50%. Run the experiment and watch it happen.
The large pizza always wins
From medium to large you don't get 33% more — you get 78%. Find out why area grows with the square.
Speeding saves less time than you think
Driving 50% faster on a 10-mile trip saves about 8 minutes. See the curve that undoes the rush.
The half nobody teaches
3 painters take 12 days. And 4 painters? If you answered 16, you fell for the inverse-proportion trap.
The raise that is a pay cut
Your salary rose 50% in 10 years and you still got poorer. Watch the ruler shrink.
The math of passing the class
Scored 55 on the first exam? Find out what you need next and where the impossible zone starts.
How long to crack your password
That 8-character password with a symbol falls in 9 hours. See why 12 plain lowercase letters are 14× stronger.
The villain on your power bill
The shower draws 5,500 W and costs R$19/month. The AC draws 1,000 W and costs R$204. See why.
What BMI can't see
The same BMI can describe an athlete or someone out of shape. See what the index measures — and what it misses.
The math that sinks small businesses
Buy at $100 and sell at $150: the margin is not 50%, it is 33%. See why the two numbers never match.
The speed you still carry when the other car stopped
Two cars brake at the same point, at 50 and 40 mph. When the 40 stops, the 50 is still doing 30. See why.
The fat-burning zone is real — and useless
Walking burns more fat than running, and running still takes off more fat. Both are true.
Three pH points, a thousand times over
Lemon (pH 2) is not "a bit" more acidic than coffee (pH 5): it is a thousand times. See why the scale misleads.
The room doubled. The floor quadrupled, the paint did not.
Double a room's dimensions: the floor quadruples and the paint only doubles. See what each change really costs.
Explore the calculators and the guides too.