You decide to put $2,000 in a savings account to save for a $3,000 downpayment on a new car. If the account has an interest rate of 4% per year and is compounded monthly, how long does it take until you have $3,000 without depositing any additional funds?

121.862 years
12.1862 years
10.155 years
1.0155 years

Respuesta :

It takes 10.155 years until you have $3,000 ⇒ 3rd

Step-by-step explanation:

The formula for compound interest, including principal sum is:

[tex]A=P(1+\frac{r}{n})^{nt}[/tex] , where

  • A is the future value of the investment/loan, including interest
  • P is the principal investment amount  
  • r is the annual interest rate (decimal)
  • n is the number of times that interest is compounded per unit t
  • t is the time the money is invested or borrowed for

∵ You decide to put $2,000 in a savings account

∴ P = 2000

∵ You want to save for $3,000

∴ A = 3000

∵ The account has an interest rate of 4% per year and is

   compounded monthly

∴ r = 4% = 4 ÷ 100 = 0.04

∴ n = 12 ⇒ compounded monthly

- Substitute all of these values in the formula above to find t

∵ [tex]3000=2000(1+\frac{0.04}{12})^{12t}[/tex]

- Divide both sides by 2000

∴ [tex]1.5=(1+\frac{1}{300})^{12t}[/tex]

∴ [tex]1.5=(1\frac{1}{300})^{12t}[/tex]

- Change the mixed number to an improper fraction

∴ [tex](1.5)=(\frac{301}{300})^{12t}[/tex]

- Insert ㏒ for both sides

∴ [tex]log(1.5)=log(\frac{301}{300})^{12t}[/tex]

- Remember [tex]log(a)^{n}=nlog(a)[/tex]

∴ [tex]log(1.5)=(12t)log(\frac{301}{300})[/tex]

- Divide both sides by [tex]log(\frac{301}{300})[/tex]

∴ 121.84 = 12 t

- Divide both sides by 12

∴ 10.155 = t

It takes 10.155 years until you have $3,000

Learn more:

You can learn more about the compound interest in brainly.com/question/4361464

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Answer:

C- 10.155 years

Step-by-step explanation:

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