SOLUTION: If an investment of 8000 earns 1280 in simple interest in 4 years, what is the rate of interest being earned? I have been able to find the answer, but I am unable to show my work.

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Question 337787: If an investment of 8000 earns 1280 in simple interest in 4 years, what is the rate of interest being earned?
I have been able to find the answer, but I am unable to show my work. I cannot figure out the proper equation formula.
Thank you

Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Simple interest only uses the principal to get interest.
I=P%2A%281%2Br%29
So the total interest divided by 4 is the interest for each year.
1280%2F4=%288000%29%281%2Br%29