SOLUTION: How many years, to the nearest year, will it take money to quadruple if it is invested at 20% compounded annually?

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Question 359737: How many years, to the nearest year, will it take money to quadruple if it is invested at 20% compounded annually?
Found 2 solutions by Fombitz, solver91311:
Answer by Fombitz(32388) (Show Source):
You can put this solution on YOUR website!

8 years.

Answer by solver91311(24713) (Show Source):
You can put this solution on YOUR website!

The formula for the future value of an investment at discretely compounded interest is:

where

represents the future value

represents the initial investment

is the interest rate as a decimal ()

is the number of compounding periods per interest term (per year for annual interest rate)

and

is the number of terms (years for annual interest rate)

You don't know or , but you do know that and that we can write the original formula as:

Next, fill in the values you know and simplify:

Take the log of both sides (base 10 or natural, doesn't matter which)

Use the laws of logs:

Divide by

The rest is arithmetic on the calculator.

John

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