### Home > CC3 > Chapter 8 > Lesson 8.1.3 > Problem 8-30

8-30.

Read this lesson’s Math Notes box about compound interest, and then answer the questions below.** **

What does the

represent in the formula? Why are the two quantities added together? Multiplying the principal amount by 1 results in the original amount. Multiplying the principal by the interest rate results in the amount gained from interest.

These values are added to calculate the percent based on the previous balance, not just the principal.

If Melanie invests

at a interest rate compounded annually, how much will she have at the end of four years?

Where

*P*is principal,*r*is the interest rate, and*n*is time.