Finance & Math guides
7 guides — practical answers with the math shown, each paired with a free calculator.
How Are Loan Payments Calculated? Amortization, Explained
One level payment, front-loaded interest — the formula worked by hand, the two levers you control, and why the smaller payment is often the costlier loan.
July 23, 2026 · 13 min read
How Does Inflation Work? The Math That Shrinks Money
One growth factor, two answers — what today's money will buy later, and how many future dollars it takes to keep up.
July 23, 2026 · 13 min read
How Is Sales Tax Calculated? Rates, Rules, and the Reverse Math
The combined-rate reality, the one-multiplication forward formula, and the division that pulls the tax back out of any total.
July 23, 2026 · 13 min read
How Much Should You Tip? Rates by Situation, With the Math
The customary rates by setting, the three-line formula, and the split order that keeps the tip at the rate you chose.
July 23, 2026 · 12 min read
How to Calculate a Discount: Sale Prices, Stacked Deals, and Tax
The percent-off formula, the sequential math behind stacked deals, and the discount-then-tax order the register actually uses.
July 23, 2026 · 13 min read
How to Calculate Take-Home Pay: From Gross to What You Keep
One combined deduction rate, your pay schedule, and a two-minute pay stub calibration — gross to net in two lines of math.
July 23, 2026 · 13 min read
How Does Compound Interest Work? The Math That Grows Money
Interest that earns interest — the formula, the frequency gap, and why steady deposits and time do most of the work.
July 20, 2026 · 7 min read