SOLUTION: If $500 is invested at 7% compounded continuously, how long would it take for the value of the investment to reach $800?

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Question 190889This question is from textbook saxon algebra 2
: If $500 is invested at 7% compounded continuously, how long would it take for the value of the investment to reach $800? This question is from textbook saxon algebra 2

Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
If $500 is invested at 7% compounded continuously, how long would it take for the value of the investment to reach $800?

The equation for continuous compounding is

A+=+Pe%5E%28rt%29

where 

P = the Principal, which is the same as the starting amount = $500
A = the AFTER amount, which is the same as the ending amount = $800
r = the rate expressed as a decimal, 0.07
t = the number of years it takes for the Principal to become the 
    AFTER amount.  That's the unknown that we want to find.
e = 2.718281828459
So we substitute everything but t in

A+=+Pe%5E%28rt%29

800+=+500e%5E%28.07t%29

Divide both sides by 500

1.6+=+e%5E%28.07t%29

Use this rule: 
The exponential equationA+=+e%5EB is equivalent to B=ln%28A%29

.07t=ln%281.6%29

Divide both sides by .07:

t+=+ln%281.6%29%2F.07

t+=+6.714337561

About 6.7 years.

Edwin