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Math, from the beginning

Money Math

Paychecks, interest, deals, and tips without a calculator.

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What this covers

Every lesson is short enough to finish in one sitting and ends with questions that make you use what you just read.

  1. Reading Your PaycheckGross, net, and where the missing money went5 min
  2. The 50/30/20 BudgetOne simple split for your take-home pay4 min
  3. Unit PricesThe shelf tag trick that beats the packaging4 min
  4. Sales and Stacked DiscountsWhy 20% off plus 10% off is not 30% off5 min
  5. Simple vs Compound InterestThe Rule of 72 and why time is the whole game6 min
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  1. Credit Cards and MinimumsWhat a statement is really telling you5 min
  2. Loans and APR IntuitionTotal cost thinking beats monthly payment thinking5 min
  3. Tips and Splitting BillsRestaurant math in your head, before the check gets cold4 min
  4. Inflation BasicsWhy the same dollars buy a little less each year5 min
  5. Spotting Bad DealsThe math tricks stores hope you skip6 min
  6. Comparing Two Job OffersHourly against salary, and everything the number leaves out8 min
  7. Interest Working For YouThe same math as debt, pointed the other direction8 min
  8. Splitting Costs FairlyThe arithmetic that decides whether people stay friends7 min
  9. Money Math Timed Simulation: Set A30 items, 30 minutes, exam mode30 min

A whole lesson, start to finish

Not a sample and not a summary. This is all of lesson 2, exactly as it reads in the app.

Lesson 2 of 14 · about 4 min

The 50/30/20 Budget

One simple split for your take-home pay

A budget is not a punishment, it is a plan for money you already have. The 50/30/20 rule is a starter split of your net (take-home) pay: 50% to needs, 30% to wants, 20% to savings and extra debt payments.

What goes where

Needs are things with real consequences if unpaid: rent, groceries, utilities, insurance, minimum debt payments, transportation to work. Wants are everything that makes life fun: dining out, streaming, hobbies, upgrades. Savings covers emergency fund, retirement, and paying debt down faster than the minimum.

Do the split in your head

Half of take-home is needs. For the other two: 30% is three times 10%, and 20% is two times 10%. On $3,000 net: 10% is $300, so wants get $900 and savings gets $600.

If your needs eat more than 50%, that is information, not failure. High rent areas do that to people. The rule flexes: maybe you run 60/25/15 for a season. The win is knowing your numbers, not hitting someone else's ratio.

The one move that matters

Automate the 20% on payday. Money that moves to savings before you see it never has to survive willpower.

Now answer the question that follows it

This is one of 3 questions on that lesson. Pick an answer and it will tell you.

The 50/30/20 rule is applied to which number?

Terms you will own

Cards come back on a schedule built from how well you knew them last time, so the ones you keep missing show up more.

More in math, from the beginning

×%Mental Math EssentialsTimes tables, tips, and percentages: the tricks school skipped 1/2Fractions & DecimalsThe bridge most of us missed, finally explained %Statistics LiteracyRead studies, polls, and headlines without being fooled

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