Guides and explainers for math, finance, and unit conversion — linked to the calculators and formulas you can use right away.
29 articles
Math guides·12 min read
A practical guide to percents as ratios out of 100 — with formulas, worked examples, and the mistakes that trip people up.
Math guides·11 min read
Evaluate expressions consistently: parentheses first, then exponents, then multiply/divide left to right, then add/subtract left to right.
Finance guides·12 min read
A fixed-rate loan payment blends interest on the remaining balance with principal repayment — early payments are mostly interest.
Finance guides·11 min read
Compound interest means you earn interest on both the original principal and on interest already added — growth accelerates over time.
29 matches
Converter guides·11 min read
Reliable conversion is factor arithmetic plus the right identity for temperature — not memorizing every pair by heart.
Product guides·8 min read
A short tour of how calculators, formulas, and converters fit together so you can solve problems faster and with more confidence.
Finance guides·10 min read
A practical guide to sale prices and sales tax: find the discount, the pre-tax total, and the final bill without mixing up the steps.
A practical guide to the three common averages: arithmetic mean, median, and mode — and how to choose the right one for your data.
A practical guide to fraction arithmetic: equivalent fractions, common denominators, and the rules for +, −, ×, and ÷.
A practical guide to writing ratios, setting up proportions, and solving for an unknown when two ratios are equal.
Percent change measures growth or decline from an original value; percent difference compares two values without treating one as “before.”
Math guides·10 min read
A practical guide to rounding decimals and counting significant figures so your answers match the precision of your measurements.
A fixed-rate mortgage payment blends interest on the remaining balance with principal repayment — and your full housing payment often includes taxes and insurance too.
An amortization schedule lists every payment’s interest, principal, and remaining balance so you can see how a loan pays down over time.
ROI compares net gain to cost as a percent — a simple scorecard for projects, ads, and investments when you define the inputs clearly.
Turn a target balance into a monthly savings plan — with or without compound interest — so your timeline and deposit size stay realistic.
APR is a nominal annual rate used widely for loans; APY (or EAR) includes compounding so you can compare true yearly growth or cost.
Converter guides·10 min read
Length conversion is multiply-or-divide by a known factor — keep units canceling and chain through meters when you lack a direct pair.
Temperature units are offset scales. Convert with the full formula — never treat Celsius ↔ Fahrenheit as a single multiply alone.
Storage labels mix decimal (1000-based) and binary (1024-based) prefixes. Knowing which system you are in prevents “missing” gigabytes.
Kitchen volume units are regional. Convert with US cup/spoon factors, weigh when precision matters, and treat oven °C/°F as true temperature conversions.
Speed units are length per time. Convert by changing the length unit, the time unit, or both — or use a single known factor such as km/h ↔ mph.
Civil time is UTC plus an offset that can change with daylight saving. Convert by shifting hours carefully and naming the zone, not only the city clock face.
Voltage, current, and resistance form Ohm’s law. Convert metric prefixes carefully, and keep V, A, and Ω matched in the same formula.
Everyday “weight” conversions on Earth use mass factors: kilograms ↔ pounds and grams ↔ ounces. Multiply or divide — and check direction.
Product guides·10 min read
Move from question → formula identity → calculator inputs → unit conversion so each tool does the job it is best at.
Product guides·9 min read
Match the job to the tool: learn with articles, recall identities with formulas, compute with calculators, and change units with converters.
A clear guide to area as covering space in square units — with the main school formulas, worked examples, and pitfalls when units or heights go wrong.
Simple interest grows in a straight line on the original principal; compound interest grows on principal plus accumulated interest. Knowing which one applies changes what you pay or earn.