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How many years will it take for $4,000 to double at a simple rate or 5%?

 Dec 11, 2014

Best Answer 

 #2
avatar+23254 
+5

If there is no compounding, it will take 20 years.

The simple interest formula:  Interest  =  Principal x rate x time

To double, the amount of interest must equal the amount of principal, so, using the formula:

                                           4000  =  4000 x 0.05 x time

                                           4000  =  200 x time

                                              20  =  time

However, not having compounding is unusual; if compounded:

The compound interest formula:  A = P(1 + r/n)^(n·t)

A = final amount = 8000        P = principal = 4000         r = rate (as a decimal) = 0.05

n = number of times compounded per year         t = time (years)

       8000  =  4000(1 + 0.05/1)^(1·t)

       8000  =  4000(1 + 0.05)^t

            2  =  (1.05)^t

      log(2)  =  t·log(1.05

             t  =  log(2) / log(1.05)  =  14.2 years

 Dec 11, 2014
 #1
avatar+7188 
0

Double is adding 100%

At a rate of 5%,  it will take 20 years because 5*20=100

I don't think there is any more work to show

 Dec 11, 2014
 #2
avatar+23254 
+5
Best Answer

If there is no compounding, it will take 20 years.

The simple interest formula:  Interest  =  Principal x rate x time

To double, the amount of interest must equal the amount of principal, so, using the formula:

                                           4000  =  4000 x 0.05 x time

                                           4000  =  200 x time

                                              20  =  time

However, not having compounding is unusual; if compounded:

The compound interest formula:  A = P(1 + r/n)^(n·t)

A = final amount = 8000        P = principal = 4000         r = rate (as a decimal) = 0.05

n = number of times compounded per year         t = time (years)

       8000  =  4000(1 + 0.05/1)^(1·t)

       8000  =  4000(1 + 0.05)^t

            2  =  (1.05)^t

      log(2)  =  t·log(1.05

             t  =  log(2) / log(1.05)  =  14.2 years

geno3141 Dec 11, 2014

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