# Investment

• Jul 16th 2009, 03:35 PM
missyd819
Investment

An investment advisor is planning the retirement of a customer. The customer has $10,000 dollars to invest and needs the investment to increase to$30,000 within 20 years...so 20 years or less.

Now I need to figure out 2 investment plans to make the above numbers work themselves out. I am so incredibly frustrated. I thought of the compound interest formula, but the problem does not tell me how many times a year the investment can or should be compounded.

Can someone please shed some light? I really need help!

• Jul 16th 2009, 04:22 PM
pickslides
$\displaystyle A=P\left(1+\frac{r}{100}\right)^t$

$\displaystyle 30,000=10,000\left(1+\frac{r}{100}\right)^{20}$

solve for r to find the required interest rate.
• Jul 16th 2009, 04:30 PM
pickslides
Also

$\displaystyle I+P = \frac{PRT}{100}+P$

$\displaystyle 20,000+10,000 = \frac{10,000\times R\times 20}{100}+10,000$

once again solve for R to find required rate using simple interest.
• Jul 17th 2009, 09:19 AM
missyd819
I have been told to use the formula A = Pe^rt.

So, I get $30,000 =$10,000 e^20r

I am unsure where to go from here????
• Jul 17th 2009, 09:32 AM
missyd819
OK, I think I got it. I got a percentage of 5.5%.

Can anyone tell me if this is correct?
• Jul 17th 2009, 11:07 AM
skeeter
Quote:

Originally Posted by missyd819
I have been told to use the formula A = Pe^rt.

So, I get $30,000 =$10,000 e^20r

I am unsure where to go from here????

$\displaystyle 30000 = 10000e^{20r}$

divide both sides by 10000 ...

$\displaystyle 3 = e^{20r}$

take the natural log of both sides ...

$\displaystyle \ln(3) = 20r$

$\displaystyle r = \frac{\ln{3}}{20} \approx 0.055$ or 5.5%

now the big question ... do you know what the formula $\displaystyle A = Pe^{rt}$ means?
• Jul 17th 2009, 11:11 AM
missyd819
YESSSS! I got the 5.5% too. I figured it out. Sooo proud of myself!! (Rofl)

I believe it means the money is continuously compounded.
• Jul 17th 2009, 12:28 PM
skeeter
Quote:

Originally Posted by missyd819
YESSSS! I got the 5.5% too. I figured it out. Sooo proud of myself!! (Rofl)

I believe it means the money is continuously compounded.

correct
• Aug 24th 2009, 04:50 PM
safaritom
Investment
Hi, I have noticed that this problem was already posted one time here, however even after reading I am still not clear on the investment plan part.
The problem states: create three investment plans for customer who has $10,000 dollars to invest and needs the investment to increase to$30,000 dollars within 20 years.
I have created a plan using Exponential Growth formula for a long term CD investment, and a Compound Interest Formula for a savings account. Now I am not sure what to use for the third plan (Thinking). Anyone? I was thinking about investing in stocks with dividents for 20 years, however not sure what formulas to apply and how. Please Help!! (Happy)

thank you
• Aug 25th 2009, 08:25 AM
Wilmer
The poor guy wants to invest $10,000 and get back$30,000
20 years later; he doesn't care HOW it's done: so why all the