Simple interest on $4120 with an annual interest rate of 3.4% for 9 years. how much did he earn in interest? round your answer to the nearest cent.

The simple interest equation is  - 

(total amount) = (starting amount) * (rate)^(time)

Let's plug in your numbers.

t = 412 * 1.034^9

(The reason I used 1.034 is because you keep the original value (1) and add 3.4% more each year (.034).)

Now you solve!

t = 412 * 1.35109177
t = 556.649809
t ≈ 556.65

So your answer is $556.65

:)