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The Magic Money Multiplier:
An Introduction to Compound Interest

APEF: Solving the Financial Illiteracy Crisis

I’m often asked, “If you could go back in time and give your younger self one tip, what would it be?” I would tell myself, “The real magic lies in compound interest, and you already have the wand – your savings account!” This might sound like something your parents talk about, but trust me, mastering this concept early can brighten your financial future.

So, what's the deal with compound interest?

Compound interest is like supercharging your money. It's not just about earning interest on your initial deposit; it's about earning interest on your interest! In simpler terms, it's money making money, and the longer it happens, the more you earn.

Why is this a big deal for high schoolers?

The earlier you start using compound interest, the more time your money has to grow. Say you save just $20 a month starting now, with 5% interest. By the time you're 30, you could have over $20,000! That's a sweet down payment on a car, a cozy nest egg for college, or a fund for your epic travel plans. The longer you wait, the smaller the snowball and the slower the ride.

The Formula:

Warning: math incoming! Don't worry, it's not as complex as it seems:

  • A is the amount of money accumulated after n years, including interest.

  • P is the principal amount (initial deposit).

  • r is the annual interest rate (as a decimal).

  • n is the number of times that interest is compounded per year.

  • t is the time the money is invested or borrowed for, in years.

Sounds interesting, but let’s take a look at a real-world example:

Let's say you invest $1,000 at a 6% interest rate, compounded monthly. Using the compound interest formula, you can calculate how much your investment will grow over time.

A=1000 x (1+0.06/12)^(12*10)

After 10 years, your investment could grow to approximately $1,819, thanks to the magic of compound interest…and that’s without making any other contributions! If you add $20/month to the initial amount, you would end up with over $5,000 in the same time period!


Quick Tip: The Rule of 72

Here's a quick hack for estimating how long it takes for your money to double with compound interest. Divide 72 by the annual interest rate, and you get an approximation of the number of years it will take for your money to double. It's a nifty trick to gauge the power of compound interest. In the example above you would divide 72 by 6 and get 12 years. Put 12 into the equation for t and voila! $2,012.20, roughly double your initial investment of $1,000. 

If you’re still not convinced that compound interest is a superpower, let’s look at some of its other advantages:

  • Long-Term Wealth Building: Compound interest rewards patience. The longer you leave your money to grow, the more it multiplies.

  • Building the Savings Habit: Even small, regular contributions can lead to significant gains over time. It encourages consistent saving.

  • Beating Inflation: Inflation erodes the purchasing power of money. Compound interest helps your savings outpace inflation, keeping your money working for you.


How can you harness this financial superpower?

  • Start small, but start now: Even $10 a month makes a difference. Every penny counts when it comes to compound interest.

  • Choose the right savings account: Look for an account with a decent interest rate to give your early investments a boost.

  • Be patient: Building wealth takes time. Don't expect overnight riches, but enjoy the satisfaction of watching your money grow steadily.

  • Automate your savings: Set up automatic transfers from your checking to your savings account, so you don't even have to think about it. Remember, out of sight, out of spend!


Understanding compound interest is like having a secret financial weapon in your arsenal. It's the force that turns small savings into substantial wealth over time. As high schoolers, you have the incredible advantage of time – use it wisely. Start saving early, watch your money grow exponentially, and set the stage for a financially empowered future. The magic of compound interest is in your hands!

Bonus Tip: Play around with online compound interest calculators to see how your savings can grow over time.

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