Pre-Calc                Notes 12/4: Natural Logs and Pert formula

 

Below are several problems that allow you to use your knowledge and problem solving skills:

 

1)      At birth, your Uncle Hans secretly purchased a $5000 U.S. Savings Bond for $2500.  The conditions of the bond state that the US Government will pay a minimum annual interest rate of r = 8.75%, compounded quarterly.  Your uncle has given you the bond as a gift, subject to the condition that you cash the bond at age 35 and buy a red Porsche.  On your way to the dealer, you receive a call from you tax accountant informing you of a 28% tax on capital gains you realize through cashing in the bond; the capital gain is the selling price of the bond minus the purchase price.  Before stepping into the showroom, compute how much cash will you have on hand, after the US Government shares in your profits.

 

 

 

 

 

 

2)    Aunt Bertha problems:

a)     She invested $2500 at 9.875% interest compounded continuously when you were 5 yrs old for your college education.  You are now 18 yrs old.  How much do you have for your education?

 

 

 

 

b)    You are now 24 yrs old and you found out that she bought a US savings bond for $1200 when you were 2 yrs old which was compounded continuously.  It is now worth $32,785.12.  What was the rate of interest?

 

 

 

 

 

c)     You are now 32 years old and you want to buy a house.  Your aunt has invested some money when your where 18 yrs old.  You checked with the bank and they told you that the interest rate was 8.75% compounded continuously and the account is worth $102,834.25.  How much did she originally invest?

 

 

 

 

3) If $2,000 is invested in a continuously compounding savings account and we want the value after 12 years to be 130,000, what is the required annual interest rate?  If instead, the same $2,000 is invested in a continuously compounding savings account with r = 6.4% annual interest, when will the exact account value be $130,000?

 

 

 

 

 

 

 

 

 

 

 

 

 

4)The earning power of men and women in the business work force can be modeled by  exponential equations.  The equation for the men's earning power is y = 9521(1.0662066)x and the women's equation y = 5616(1.0727495)x.  Determine when the earning power of the women will exceed the men's.