SOLUTION: Mario decided to invest his $620 tax refund rather spending it. He found a bank that would pay him 4% interest, compounded quarterly. Mario deposits the entire $620 refund and does

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Question 432116: Mario decided to invest his $620 tax refund rather spending it. He found a bank that would pay him 4% interest, compounded quarterly. Mario deposits the entire $620 refund and does not deposit or withdraw any other amount.
a. write an equation that models the growth of the investment.
b. how many years will it take for the initial investment to double?
Found 2 solutions by solver91311, jorel1380:
Answer by solver91311(24713)   (Show Source): You can put this solution on YOUR website!




Where is the future value, is the present value, is the annual interest rate as a decimal, is the number of compounding periods per year, and is the number of years.

For your situation, just plug in the given numbers:



For the principal to to double, has to be 2 times , hence



Just solve the exponential equation for

John

My calculator said it, I believe it, that settles it
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Answer by jorel1380(3719)   (Show Source): You can put this solution on YOUR website!
Given 4% compounded quarterly, the yearly rate is 4.06%.
a)Amount=$620+.0406^X(620) where X is the number of years the money is left in the account
b)At this rate, Mario's money will double in approximately 18 years.
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