Simple vs Compound Interest: Formulas and Examples
Both formulas, worked examples in years, months and days, a side-by-side table, and the rule of 72.
4 Function Calculator Blog
Practical arithmetic tutorials, calculator shortcuts, and computational insights designed to help you calculate faster, smarter, and with complete confidence.
Margin vs Markup: What's the Difference and How to Price
The two formulas, converting between them, pricing for a target margin, and how discounts eat into profit.
How to Calculate GPA: Semester, Cumulative and Weighted
Quality points and credits, weighted honors and AP classes, cumulative GPA, and how far one term can raise it.
How to Calculate Your Grade (and What You Need on the Final)
Points to percent, letter grades and GPA, weighted categories, the final exam score you need, and how many questions you can miss.
How to Round Numbers: Place Values, Decimals and Significant Figures
The one rule behind rounding, carrying 9s, significant figures, banker's rounding and the double-rounding trap.
Ratios and Proportions: How to Simplify, Solve and Share
Simplify ratios, solve proportions by cross-multiplying, share amounts fairly, and scale recipes and maps.
How to Convert Fractions to Decimals (and Back)
Long division or powers of 10, when a decimal will repeat, and how to turn any decimal, even a repeating one, into a fraction.
GCF vs LCM: How to Find Them and When to Use Each
Listing, prime factorization and Euclid's algorithm, plus how to tell which one a word problem needs.
How to Do Long Multiplication: Steps, Carrying and Examples
Carrying, placeholder zeros, the box method, decimals and negatives, with worked examples and practice problems.
How to Do Long Division: Steps, Examples and Practice
Divide, multiply, subtract, bring down: worked examples with one- and two-digit divisors, zeros, remainders and decimals.
How to Compare Prices by Unit Price: A Shopping Guide
Read shelf tags, convert units in your head, spot when a sale changes the best deal, and think in cost per use.
Mean vs Median: Which Average Should You Use?
When the mean and median agree, how outliers pull the mean, and which average to trust for incomes, prices and grades.
Order of Operations Practice Problems With Answers
10 PEMDAS problems in 3 levels, each with a worked answer you can check step by step in the calculator.
How to Calculate a Tip in Your Head: 15%, 18%, 20% & More
Build any tip from 10% in seconds, split a tip fairly, and handle coupons, tax and service charges.
How to Calculate Sales Tax: Formulas, Shortcuts & Examples
Add tax, take it out of a total, handle odd rates like 8.875%, estimate it in your head, and budget with tax included.
How to Calculate a Discount: Sale Prices, Coupons & Deals
Find sale prices in your head, stack coupons correctly, compare dollars-off with percent-off, and decode multi-buy deals.
Percent Change vs Percentage Points vs Percent Difference
Three ways to compare numbers with percents, when to use each, and the traps that make small changes sound huge.
How to Calculate a Percentage: 3 Formulas & Examples
The three percent formulas, mental-math shortcuts, percent increase and decrease, and practice problems with answers.
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