SOLUTION: Compound Interest. Suppose that $750 is invested at 7% interest, compounded semiannually. a) Find the function for the amount to which the investment grows after t years. b) Fin

Algebra ->  Logarithm Solvers, Trainers and Word Problems -> SOLUTION: Compound Interest. Suppose that $750 is invested at 7% interest, compounded semiannually. a) Find the function for the amount to which the investment grows after t years. b) Fin      Log On


   



Question 830810: Compound Interest. Suppose that $750 is invested at 7% interest, compounded semiannually.
a) Find the function for the amount to which the investment grows after t years.
b) Find the amount of money in the account at t=1,6,10,15, and 25 years.
Please help!

Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
a) 7% anual interest compounded semiannually means that every 6 months
%227+%25%22%2F2=%223.5+%25%22 interest is added to the balance.
That is %223.5+%25%22=3.5%2F100=0.035 times the balance
After 6 months, you have
$750%2B750%2A0.035=$750%2A%281%2B0.035%29=$750%2A1.035 .
You started with $750, but the calculation is the same for any other number.
In 6 months the amount grows by a factor of 1.035 .
Six month later, at the 1 year mark, that $750%2A1.035 amount gets multiplied times 1.035 again,
so after one year you have $750%2A1.035%5E2.
That multiplication times 1.035%5E2 happens every year, so after t years you have
$750%2A%281.035%5E2%29%5Et=$highlight%28750%2A1.035%5E%282t%29%29

b) For t=1 , the amount is 750%2A1.035%5E2=750%2A1.071225=highlight%28803.42%29 (rounded).
For t=6 , the amount is 750%2A1.035%5E12=750%2A1.511069=highlight%281133.30%29 (rounded).
For t=10 , the amount is 750%2A1.035%5E20=750%2A1.989789=highlight%281492.34%29 (rounded).
For t=15 , the amount is 750%2A1.035%5E30=750%2A2.806794=highlight%282105.10%29 (rounded).