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Melissa invested $500 in a savings account the pays an annual interest rate of 3.5% compounded continuously. How long will it take for her savings to reach $650. 

 

I know this uses the A=Pe^rt formula but I only know P=500, r=3.5, A=650... If I am right, there are still ones which I don't know.

 

Please explain how to solve this. thankyou :) <3

 Mar 15, 2016

Best Answer 

 #2
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Solve for t over the real numbers:
650 = 500 e^(0.035 t)

500 e^(0.035 t) = 500 e^(7 t/200):
650 = 500 e^((7 t)/200)

650 = 500 e^((7 t)/200) is equivalent to 500 e^((7 t)/200) = 650:
500 e^((7 t)/200) = 650

Divide both sides by 500:
e^((7 t)/200) = 13/10

Take the natural logarithm of both sides:
(7 t)/200 = log(13/10)

Multiply both sides by 200/7:
Answer: |  t = 200/7 log(13/10)=7.50 Years.

 Mar 15, 2016
 #1
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0

Ah, I just remembered e = 2.718 

 

Whoever considered solving this, how nice of you smiley <3 thankyou, there's no need to solve it anymore~ I just understood it

 Mar 15, 2016
 #2
avatar
+5
Best Answer

Solve for t over the real numbers:
650 = 500 e^(0.035 t)

500 e^(0.035 t) = 500 e^(7 t/200):
650 = 500 e^((7 t)/200)

650 = 500 e^((7 t)/200) is equivalent to 500 e^((7 t)/200) = 650:
500 e^((7 t)/200) = 650

Divide both sides by 500:
e^((7 t)/200) = 13/10

Take the natural logarithm of both sides:
(7 t)/200 = log(13/10)

Multiply both sides by 200/7:
Answer: |  t = 200/7 log(13/10)=7.50 Years.

Guest Mar 15, 2016
 #3
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0

thankyou :)

lekRJtj  Mar 15, 2016

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