Math Help???????

Question

Find how long it takes $2000 to double if it is invested at 7% interest compounded semiannually.

Use the formula

 

A=P  (  1- r/n) nt  to solve the compound interest problem

 

It will take approximately ????? years

Answer 1

Hello, thank you for taking the time to post your question!

Since the question is asking about compound interest, the underlying formula you want to use here is

A = P(1 + r/n)^(nt)

In this scenario we’re plugging in A = 2000*2 = 4000, P = 2000, r = 7% = 0.07, n = 2, and then solving for the value of t algebraically

4000 = 2000(1 + 0.07/2) ^ (2t)

2 = (1.035)^(2t)

ln (2) = 2t * ln(1.035)

t = ln(2) / 2 * ln(1.035) = 10.07

meaning that the amount will double in about 10.07 years

I hope that helps you get moving in a better direction on this type of question! Feel free to reach out if you have any additional questions beyond that :)

Answer 2

I answered on the other question you asked. Double-check the formula you put here, as I think it needs a plus sign, in the parentheses. 

 

Also, use the other problem to guide you through this one. I hope you'll share your work, so we can help you through this one if you get stuck. :)