SOLUTION: Lili invests $15,000 in two one-year certificates of deposit. One certificate pays 3%, and the other pays 3.5% simple interest annually. (a) Construct a model for the total inte

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Question 1118791: Lili invests $15,000 in two one-year certificates of deposit. One certificate pays 3%, and the other pays
3.5% simple interest annually.
(a) Construct a model for the total interest I(x) Lili earns in one year on her investments. (Let x represent the amount invested at 3%.)
(b) If Lili's total interest is $510.00, how much money did she invest in each certificate?
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!


Let represent the amount invested at 3%, then the amount invested at 3.5% must be because the sum of the two investments is given as $15,000.

The amount of interest earned in one year on dollars at 3% presuming annual compounding is , whereas the amount of interest earned in one year at 3.5% on dollars is . Hence the dollar amount of the interest earned as a function of the amount invested at 3% is:



Then, if you are given that , solve the equation:



for and then calculate


John

My calculator said it, I believe it, that settles it