math
Math
Percentages, fractions, statistics, geometry, and practical math explainers.
The Math category makes practical mathematics approachable for everyday use. Articles cover percentage change, fraction operations, ratio and proportion, scientific notation, and standard deviation. Each guide breaks down the formula step by step, provides multiple worked examples, and includes reference tables for common values. Whether you are calculating a grade, interpreting statistical data, or converting between fraction and decimal forms, these guides provide the foundation you need before using the corresponding calculator tool.
21 articles in this category
Cross Multiplication: A Beginner's Guide for Students & Teachers
Master cross multiplication with the "butterfly method," step-by-step worked examples, practice questions with answers, common mistakes, and real-world applications.
How to Find the Midpoint: Step-by-Step Guide for Students & Teachers
Master the midpoint formula with step-by-step worked examples, learn how to find a missing endpoint, practice questions with answers, common mistakes, and real-world applications.
Long Division Word Problems: Easy, Medium & Hard Examples with Real-World Practice
Practice long division with real-world word problems graded from easy to hard, learn how to handle decimal answers, know when to round remainders up or down, and check your work against every answer.
Long Division in Real Life: Bills, Recipes, Budgets, Sports & More
See long division at work outside the classroom — splitting a restaurant bill, scaling a recipe, budgeting monthly expenses, calculating a sports average, comparing unit prices, and more, with fully worked real-world examples.
Long Division with 2-Digit, 3-Digit & Decimal Divisors: Advanced Techniques
Master long division once the divisor itself gets bigger — 2-digit and 3-digit divisors, decimal divisors, and how to estimate quotient digits quickly, with fully worked examples and a dedicated mistakes checklist.
How to Find Slope: 3 Methods for Points, Graphs & Equations (Plus the 4 Types of Slope)
Find the slope of a line three different ways — from two coordinate points, by counting on a graph, or by reading it straight from an equation — and learn to identify positive, negative, zero, and undefined slope on sight.
Cross Multiplication Word Problems: 12 Real-World Examples with Step-by-Step Solutions
The hard part of a proportion problem is rarely the cross multiplication itself — it is translating the words into a fraction = fraction setup. 12 fully worked examples across recipes, maps, dosages, chemistry, sports, and more.
Midpoint Riemann Sum: A Step-by-Step Guide for Calculus Students
Master Riemann sums with step-by-step instructions for Left, Right, Midpoint, and Trapezoidal methods, worked calculus examples, over/under estimation guides, practice questions, and AP exam strategies.
Long Division: A Complete Guide for Students & Mental Math Enthusiasts
Master the traditional long division method step by step, then learn the cross division technique for dividing large numbers entirely in your head, with worked examples and practice problems.
Simplifying Fractions: Step-by-Step Guide for Students & Teachers
Master simplifying fractions using the GCF method, prime factorization, and repeated division, plus fractions with variables and exponents, practice questions, and real-world applications.
How to Calculate Slope Incline: A Complete Guide for Students & Professionals
Master the slope formula (rise over run), convert between ratio, percentage, decimal, and angle formats, and apply slope incline to roads, ramps, roofs, and drainage with worked examples.
Standard Deviation Guide: Measure Data Spread Clearly
Understand variance, population vs sample formulas, and data spread with worked examples tied to the live DTC standard deviation calculator.
Scientific Notation Guide: Powers of Ten Made Practical
Learn how to convert, compare, and calculate with powers of ten using worked examples and the live DTC scientific calculator.
Ratio and Proportion Guide: Simplify, Solve, Split Totals
Learn how to simplify ratios, solve proportions, and split totals with worked examples tied to the live DTC ratio calculator.
Fraction Operations Guide: Add, Subtract, Multiply, Divide
Learn the rules for adding, subtracting, multiplying, and dividing fractions, with simplification steps and live DTC calculator workflows.
Percentage Change Guide: Increase, Decrease, Difference
Learn when to use percent of, percent change, and percent difference with worked examples tied to the live DTC percentage calculator.
Triangle Geometry Guide: Area, Perimeter, Heron Formula
Learn triangle validity, perimeter, semi-perimeter, and Heron formula area with worked examples tied to the live DTC triangle calculator.
Unit Conversion Guide: Length, Weight, Temperature
Learn dimensional analysis and practical unit conversion for length, weight, and temperature with examples tied to the live DTC unit converter.
Date Arithmetic Guide: Differences, Deadlines, and Calendar Math
Learn how date arithmetic works, how the DTC date calculator measures elapsed days, and why calendar intervals, deadlines, and age-style borrowing need clear rules.
Time Calculation Guide: Adding, Subtracting, and Converting Durations Correctly
Learn how to add and subtract time durations, convert total minutes into hours and decimal hours, and understand what the current DTC time calculator does well and where you should switch to hours or date-based tools.
Random Number Generation Guide: Seeded PRNGs, True Randomness, and Safe Use Cases
Learn the difference between deterministic seeded generators, browser pseudo-random functions, and cryptographically strong randomness so you can use the right tool for the job.
Explore other categories
Finance
Mortgages, loans, savings, investing, debt payoff, retirement, and tax planning guides with worked examples.
Browse FinanceHealth
BMI, calories, macros, hydration, pregnancy, and wellness calculator guides.
Browse HealthBusiness
Rates, margins, break-even math, taxes, invoices, and small-business planning.
Browse BusinessMath calculators
Popular math calculators
Use these calculators alongside the guides above to run the numbers for your specific situation.
Scientific Calculator
Calculate advanced arithmetic, trigonometry, logarithms, and exponential functions instantly with this free scientific calculator.
Fraction Calculator
Add, subtract, multiply, divide, and simplify fractions instantly with this free step-by-step online fraction calculator tool.
Triangle Calculator
Solve triangle sides, angles, area, and perimeter instantly using this free step-by-step online triangle geometry calculator.
Random Number Generator
Generate random numbers within a custom minimum and maximum range instantly with this free online random number generator.
Standard Deviation Calculator
Calculate mean, variance, and standard deviation for any dataset instantly with this free step-by-step statistics calculator.
Percentage Calculator
Solve percentage changes, ratios, increases, and differences instantly with this free and easy percentage calculator tool.
FAQ
Frequently asked questions
How do I calculate percentage change?+
Percentage Change = (New Value — Old Value) ÷ Old Value × 100. A positive result means an increase, negative means a decrease. Use our Percentage Change Calculator for quick results.
What is standard deviation telling me?+
Standard deviation measures how spread out numbers are from the average. A low standard deviation means values cluster close to the mean; a high standard deviation means they are widely dispersed. Use our Standard Deviation Calculator to analyze your data set.
How do I calculate the area of a triangle?+
The most common formula is Area = ½ × base × height. If you only know the three side lengths, use Heron Formula. Our Triangle Calculator supports both methods and more.