(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

So I'm going over the simple yearly interest formula A=P(1+r)^t, where 't' is in years, 'P' is in dollars and is the size of the initial investment, 'A' is in dollars and is the total interest earned in a given period of years, and 'r' is the rate at which the investment grows.

I've done countless problems involving this and more complicated interest formulas. What I don't understand: How do I account for the variable 't', specifically its units, in the final answer, given that I'm looking for the total interest earned, which is in dollars? Where does the unit 'years' go?

2. Relevant equations

Interest Accumulated = A = P(1+r)^t

3. The attempt at a solution

Ex: Find the interest earned on a $750 dollar principal invested for 5 years at an interest rate of 9%.

A=(750dollars)(1.09)^(5years)=(1153.97dollars) <-- My current understanding is that I can just consider the final answer as being in dollars because the units for the exponent are only there as a guide through the problem. On top of that I don't consider 'r' as having any units because it's just a decimal number used to modify P. Both of these explanations are arbitrary and I've learned those don't usually work in math. Can someone give me some guidance?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Exponents that have units (how to deal with them)

**Physics Forums | Science Articles, Homework Help, Discussion**