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Math for Real Life
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Percentages, growth, averages and chance: the math behind your money, your health and your choices.
3h 26m6 constellations
01Handle percentages and percentage changes without traps
02Compare prices, rates and growth over the same period
03Read averages, samples and risks without being fooled
04Estimate anything to the right order of magnitude
Every lesson of Math for Real Life
18 lessons in 6 levels, about 3 hours. Level 1 is free.
Level 1Percentages Without FearFree · 3 lessons
- Percent means “per hundred”Solve the three kinds of percentage questions, in your head when you need to.10 min
- Up 50%, down 50% isn't evenChain and reverse percentage changes correctly by turning them into multipliers.11 min
- Checkpoint: “doubles the risk”, from what?Translate relative changes into absolute numbers, and percent into percentage points.12 min
Level 2Ratios, Rates and UnitsMembership · 3 lessons
- Compare prices per unitCompare packs, bottles and deals by their price per unit, and spot shrinkflation.10 min
- Scale anythingScale recipes, maps and prices, and recognize when two quantities are not proportional.11 min
- Checkpoint: rates that fool everyoneAvoid the average-speed trap and the MPG illusion by averaging over the right thing.12 min
Level 3Lines and CurvesMembership · 3 lessons
- Your brain draws straight linesTell linear from exponential growth, and feel how fast doubling runs away.11 min
- The rule of 72Turn any growth rate into a doubling time in your head.10 min
- Checkpoint: per what, and from what?Convert rates to the same period and look for the base behind any growth claim.12 min
Level 4Averages and SpreadMembership · 3 lessons
- Mean, median and the billionaire in the caféChoose the average that describes the typical case, and spot skewed data.10 min
- Averages hide the spreadAsk for the spread as well as the average, and see why plans built on averages run late.11 min
- Checkpoint: small samples swing moreCheck sample sizes before trusting extreme results, and read a poll's margin of error.12 min
Level 5Chance and RiskMembership · 3 lessons
- Chance, “at least one” and birthdaysCombine probabilities for “and” and “at least one”, and resist the gambler's fallacy.11 min
- Test results: think in peopleWork out what a positive result means by imagining 1,000 people.12 min
- Checkpoint: read any risk claimQuestion any claim with five checks, and compute the number needed to treat.13 min
Level 6Numbers in the WildMembership · 3 lessons
- Charts that misleadRead the axes before the shape, and spot the common distortions.11 min
- Estimate anythingBreak an unknown quantity into factors you can guess, and land on the right order of magnitude.12 min
- Capstone: the numbers behind a decisionRun a real decision through every tool in the path.15 min
AFTER THE CORE