Respuesta :
Answer:
Equation is A = 5000(1.015)^(4t)
Her investment will be worth $10,000 in about 11.63888 years
Rounding up to the nearest whole number gets to 12 years
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Explanation:
Part 1) Finding the equation
The compound interest formula is
A = P(1+r/n)^(n*t)
Here are the variables
- A = final amount
- P = starting amount, or deposit, or principal
- r = interest rate in decimal form
- n = number of times money is compounded per year
- t = number of years
In this case,
- P = 5000
- r = 0.06 from the 6% annual interest
- n = 4 times a year is the compounding frequency
- t = unknown amount of time
Therefore, the equation is
A = P(1+r/n)^(n*t)
A = 5000(1+0.06/4)^(4t)
A = 5000(1.015)^(4t)
The decimal value is exact.
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Part 2) Let's plug in A = 10,000 and solve for t.
You'll need to use logarithms to isolate the exponent.
A = 5000(1.015)^(4t)
10,000 = 5000(1.015)^(4t)
10,000/5000 = (1.015)^(4t)
2 = (1.015)^(4t)
Log[ 2 ] = Log[ (1.015)^(4t) ]
Log(2) = 4t*Log( 1.015 )
4t = Log(2)/Log(1.015)
4t = 46.5555256308062
t = 46.5555256308062/4
t = 11.6388814077015
t = 11.63888
It takes about 11.63888 years for the investment to reach $10,000.
Therefore, at the 12 year mark is when the investment is more than $10,000.
Answer:
11 years and 9 months
Step-by-step explanation:
Compound Interest Formula
[tex]\large \text{$ \sf A=P(1+\frac{r}{n})^{nt} $}[/tex]
where:
- A = final amount
- P = principal amount
- r = interest rate (in decimal form)
- n = number of times interest applied per time period
- t = number of time periods elapsed
Given:
- A = $10000
- P = $5000
- r = 6% = 0.06
- n = 4 (as compounded quarterly)
- t = years
Substitute the given values into the equation and solve for t:
[tex]\implies 10000=5000\left(1+\dfrac{0.06}{4}\right)^{4t}[/tex]
[tex]\implies \dfrac{10000}{5000}=\left(1+0.015\right)^{4t}[/tex]
[tex]\implies 2=\left(1.015\right)^{4t}[/tex]
Take natural logs of both sides:
[tex]\implies \ln 2=\ln \left(1.015\right)^{4t}[/tex]
Apply the power log law:
[tex]\implies \ln 2=4t\ln \left(1.015\right)[/tex]
Simplify:
[tex]\implies t=\dfrac{\ln 2}{4 \ln 1.015}[/tex]
[tex]\implies t=11.63888141[/tex]
11.6388141... years ≈ 11 years and 7.7 months
As the interest is earned quarterly, round this to the nearest quarter
⇒ 11 years and 9 months.
Therefore, Kim's investment will be worth more than $10,000 at 11 years and 9 months.