Solving for time (use your custom formula :-)
4) Find the time in years required to pay off a loan with the given terms:
P = $16,425, R = $500, r = 9% compounded monthly
5) To purchase a $23,620 swimming pool, a family makes a 10% down payment and
finances the remainder with a loan at 8.3% interest compounded quarterly. If they make
loan payments of $2000 per quarter, how long will it take them to pay off the loan?
6) Suppose $10,000 is borrowed at 8.7% interest compounded monthly.
a) How long will it take to pay off the loan with monthly payments of $200?
b) How long will it take to pay off the loan with monthly payments of $100?
c) What happens if you use the loan formula to find out how long it will take to pay off the
loan with monthly payments of $50? Why does the formula not work in this case?
(#1)
F = P(1 + rt)
(#2)
(#3)
(#4)
$F = P \left(1 + \frac{r}{n} \right)^{nt}$
$F = D \left( \frac{\left(1 + \frac{r}{n} \right)^{nt} - 1}{\frac{r}{n}} \right)$
$P = R \left( \frac{1 - \left(1 + \frac{r}{n} \right)^{-nt}}{\frac{r}{n}} \right)$
(#5)
(#6)
(#7)
(#8)
$r = n \left( \left( \frac{F}{P} \right)^{1/nt} - 1 \right)$
$t = \frac{\log \left( \frac{F}{P} \right)}{n \log \left(1 + \frac{r}{n} \right)}$
$t = \frac{\log \left( \frac{D}{R} \left( \frac{r}{n} \right) + 1 \right)}{n \log \left(1 + \frac{r}{n} \right)}$
$t = \frac{\log \left( - \frac{P}{R} \left( \frac{r}{n} \right) + 1 \right)}{-n \log \left(1 + \frac{r}{n} \right)}$
21q