What Math 125 Taught Us About Auto Loans, Interest Rates, and Refinancing | Dee & Dee Brown LLC

Most people sign auto loan paperwork without fully understanding how much interest they will actually pay over time.

In Math 125 at Washtenaw Community College, we started calculating those numbers ourselves—and it completely changed how we think about borrowing money, refinancing, and long-term financial decisions. 

When we first started working through car loan calculations in Math 125 at Washtenaw Community College, it honestly felt repetitive. Monthly payments. Finance charges. Installment pricing. Interest formulas. At first, it seemed like just another set of math problems. But then we realized something important: these numbers affect real people every single day.

For us at Dee & Dee Brown LLC, Math 125 stopped being “just math” once we connected it to something real: auto loans, refinancing, and the true cost of borrowing money.

The Real Cost of a Car Loan

Most people shop for a vehicle based on one thing:

“Can I afford the monthly payment?”

But Math 125 teaches something deeper. A lower monthly payment does not always mean a better financial decision. In many cases: lower payments, longer loan terms, and higher interest rates…can quietly cost thousands more over time.

That is why understanding: finance charges, total installment price, and interest rates matters so much.

The Dee & Dee Brown LLC Connection

As a mother-daughter team building Dee & Dee Brown LLC, we started looking at our own financial systems differently. We began asking:

"Are we paying too much in interest?"
"Would refinancing help us?"
"What numbers actually matter to lenders?"
"How does credit affect long-term costs?"

That brought us directly back to the same formulas we are learning in Math 125. Suddenly, the lessons became personal.

From 1988 to 2024: What Changed

In May 1988, Donnetta Brown purchased her first new car, a 1988 Ford Festiva. 

At the time, the focus was simple: getting approved, making the payment, and having reliable transportation. Like many people, the deeper financial details behind the loan—interest rates, finance charges, and the true long-term cost of borrowing—were not fully understood yet. 

Decades later, while studying loan calculations in Math 125 at Washtenaw Community College, that experience took on new meaning. 

Looking back at this photo now represents more than a first car purchase. It represents growth, financial awareness, and the journey from simply signing a contract to truly understanding how financing decisions affect long-term financial stability.

Our Current Transportation Reality

Donnetta and Dominique Brown beside their 2021 Mazda CX-30 after signing their current vehicle lease agreement in February 2024.

More than three decades after purchasing her first vehicle, Donnetta is now analyzing financing decisions from an entirely different perspective alongside her daughter Dominique. 

Leasing, refinancing, credit scores, finance charges, and long-term borrowing costs now play a much bigger role in how we evaluate transportation decisions for both personal and business stability.

What We Understand Now That We Didn’t Understand Then

Before studying financing calculations in Math 125, transportation decisions mostly centered around one question:

“Can we afford the monthly payment?”

Now we understand that the monthly payment is only part of the story.

What matters just as much is: the interest rate, the length of the loan, the total installment price, and the long-term finance charge. A lower payment can sometimes mean paying far more over time because of extended loan terms and higher interest costs.

We also understand how credit scores, debt balances, and vehicle value affect refinancing opportunities and lender approval decisions. That shift in thinking changed how we view borrowing money—not just personally, but as entrepreneurs building Dee & Dee Brown LLC.

Instead of focusing only on affordability today, we now think about: long-term financial stability, cash flow, total borrowing costs, and how financial decisions affect future business growth. Math 125 helped us realize that financial literacy is not just about passing a class. It is about making smarter decisions that protect both personal and business finances over time.

As we worked through real Math 125 financing problems by hand, we started seeing how finance charges, interest rates, and installment pricing affect long-term borrowing costs in ways many people do not initially realize.

Solving these problems step-by-step helped us better understand how lenders calculate borrowing costs and why two loans with similar monthly payments can have very different long-term financial consequences.

What We Learned About Refinancing an Auto Loan

Refinancing sounds simple: replace your current loan with a new one.

But lenders are looking closely at your numbers before approving you. They review: credit score, vehicle value, loan balance, income, and payment history.

One of the most important formulas is the Loan-to-Value Ratio (LTV).

Loan-to-Value Formula

$\mathrm{<span\; style="font-family:\; arial;"><span\; style="font-size:\; medium;"><b>L</b></span></span>}\mathrm{<span\; style="font-family:\; arial;"><span\; style="font-size:\; medium;"><b>T</b></span></span>}\mathrm{<span\; style="font-family:\; arial;"><span\; style="font-size:\; medium;"><b>V</b></span></span>}<span\; style="font-family:\; arial;"><span\; style="font-size:\; medium;"><b>=</b></span></span>\frac{\text{<span style="font-family: arial;"><span style="font-size: medium;"><b>Loan Balance</b></span></span>}}{\text{<span style="font-family: arial;"><span style="font-size: medium;"><b>Vehicle Value</b></span></span>}}<span\; style="font-family:\; arial;"><span\; style="font-size:\; medium;"><b>\times </b></span></span>\mathrm{<span\; style="font-family:\; arial;"><span\; style="font-size:\; medium;"><b>100</b></span></span>}$

This formula helps lenders determine risk. If you owe more than the vehicle is worth, refinancing becomes much harder. That was a major real-world connection for us.

Why Interest Rates Matter More Than People Realize

A small difference in interest rate can change the total cost of a vehicle dramatically. For example: a higher interest rate combined with a longer term can increase the finance charge by thousands of dollars.

Math 125 teaches students how to calculate: interest, total payments, and installment costs. In real life, those calculations determine: affordability, approval chances, and financial flexibility.

The Bigger Lesson About Financial Literacy

This class is teaching more than formulas. It is teaching awareness.

At Dee & Dee Brown LLC, we realized that entrepreneurs must understand: borrowing, interest, financing, and long-term repayment costs.  A business can lose money quietly through:

• high-interest loans,
• unnecessary refinancing,
• poor credit decisions,
• and expensive monthly payments.

Understanding the math behind financing helps protect both personal and business finances.

Why This Matters for Entrepreneurs

Transportation affects business operations. For resellers and entrepreneurs, vehicle costs impact:

• inventory pickups,
• sourcing trips,
• shipping schedules,
• customer service,
• and overall cash flow.

That means understanding car loans is part of understanding business management.

Math 125 helped us see that financial literacy is not optional. It is part of building a stable future. Before this course, we mostly looked at financing emotionally:

“Can we afford the payment?”

Now we ask:

"What is the total borrowing cost?"
"How much interest are we really paying?"
"Does refinancing actually help?"
"What are the long-term consequences?"

That mindset shift matters. For Dee & Dee Brown LLC, Math 125 is helping us connect education to real financial decision-making. We are not just solving equations anymore.

We are learning how to think differently about money, debt, and long-term business growth. Follow Dee & Dee Brown LLC as we connect college, entrepreneurship, and real-world financial systems one lesson at a time.

Learning. Applying. Building.