MAT-144 · Mathematical Reasoning Video Library

ORBITAL Mini Lessons

Every video, cross-referenced with every lesson.

Short evergreen explanations — about three minutes each — that sit alongside the mini lessons and pack the same math tighter. Open a topic, or search across every title. Missing videos are on the way; the catalog shape shows what’s coming.

Every video, cross-referenced with every lesson.

What, Exactly, Is a Function?

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Playlists

Top 10 · Exam 1 walkthroughs

Percent of a Total Without Reaching for the Calculator

Percent Off or Money Back? Comparing Two Deals

Why Two Discounts Never Add Up

Working a Percent Backwards to the Original

Finding the Percent When You Have Both Numbers

The Volume Ladder: Gallons Down to Fluid Ounces

Inches In, Square Feet Out: Area, Whole Tins, and Cost

Count First, Convert Once

Unrolling Four Walls Into One Rectangle

Which Way Up? Reading Units, Not Numbers

Topic 1 · Linear Functions

What, Exactly, Is a Function?

The Two Ways Humans Reason

Close Enough Is a Superpower

Slope Is Just "How Fast"

One Equation. Predict the Future.

A Spreadsheet Is a Grid of Functions

What Is the y-Intercept, Really?

y = mx + b Is a Machine

The Point-Slope Formula, Explained

Parallel and Perpendicular, in One Picture

Two Points Define a Line

How to Find the Equation of a Line Through Two Points

Linear Model Application: Writing an Equation From a Word Problem

f(x) Is Not f Times x

Domain and Range, in Plain English

The Vertical Line Test, Explained

Find f(3) With No Formula

Where Two Lines Meet

Slope Zero vs Slope Undefined

Negative Slope Isn't Bad

Ax + By = C, Decoded

Topic 2 · Conversions & Budgeting

Percent Just Means "Out of 100"

One Number, Three Disguises

Tip, Tax, Discount: One Move

Multiply by 1, Convert Anything

60 mph Is How Many Feet per Second?

Tell Your Money Where to Go

Percent vs Percentage Points (4% to 6% Is Up 50%)

Stacking Discounts: Why 50% Off Twice Isn't Free

Percent Change Trap: Up 50% Then Down 50% Is a Loss

How to Find the Original Price Before Tax or Discount

How to Add Measurements With Different Units

How to Convert Square Units: Square Yards to Square Feet

How to Convert Fahrenheit to Celsius (and Why It's Weird)

Topic 3 · Savings

What Is Interest? It's Rent on Money

Simple Interest Explained: I = Prt in One Multiply

Compound Interest Explained: Interest That Earns Interest

APR vs APY Explained: The Rate You Actually Earn

What Is an Annuity? Many Payments, One Formula

Future Value of an Annuity: $200 a Month Becomes $244,000

The Rule of 72 Explained: How Long to Double Your Money

Compound Interest: Continuous Compounding Explained

Compound Interest: Finding Interest Earned Between Two Years

Present Value Explained: What Future Money Is Worth Today

Compound Interest: Saving at 25 vs 35 Compared

Sinking Funds Explained: How Much to Save per Month

Topic 4 · Loans

What Is Amortization? Where Loan Payments Actually Go

How to Calculate a Loan Payment (Monthly Payment Formula)

How Car Loans Work: Monthly Payment and Total Interest

Credit Card Minimum Payments: Why You Stay in Debt

Subsidized vs Unsubsidized Student Loans: The Difference

How Mortgage Payments Work: Interest vs Principal

How Much House Can You Afford? (The 28/36 Rule)

Rent vs Buy: The Real Monthly Cost of Owning a Home

What Is PMI? Private Mortgage Insurance Explained

When Should You Refinance? The Break-Even Formula

How Down Payments Work: Why Bigger Saves You Twice

15 vs 30 Year Mortgage Explained: Payment vs Total Cost

APR vs Interest Rate: What's the Difference?

Extra Mortgage Payments Explained: Years and Interest Saved

Biweekly Mortgage Payments: Do They Really Save Money?