Final answer:
By setting up an equation based on the given interest rates and total interest, we can determine that Lynn Ogen invested $400.00 at 7% interest.
Step-by-step explanation:
Lynn Ogen invested an unknown amount of money at 9% interest and $100 less than that amount at 7% interest, with her total annual interest being $73.
Let's define x as the amount of money invested at 9%. Then, the amount invested at 7% would be x - $100. To find the interest earned from these investments, we use the interest formula:
Interest = Principal × Rate × Time
Since the time is presumably 1 year based on the phrasing of the question, we can simplify this to:
Interest = Principal × Rate
Adding the interest earned from both rates, we have:
0.09x + 0.07(x - 100) = $73
Solving this equation, we get:
0.09x + 0.07x - 7 = 73
0.16x = 80
x = $500
Therefore, the amount invested at 7% would be:
x - $100 = $500 - $100
$400
So, Lynn invested $400.00 at 7%, which corresponds to option A.