Credit Cards

build up your credit score

can give rewards like "cash back"

offers unlimited money

protection against fraud

live off the grid

run

use multiple credit cards

pay off your credit cards completely so that no money builds up

$k\ =\ \frac{y}{x}$

$k=\frac{x}{y}$

$y=\frac{k}{x}$

$k\ =\ \frac{y}{x}$

$k=\frac{x}{y}$

$y=\frac{k}{x}$

 $x=\frac{y}{k}$  

 $money\ on\ card=\frac{total\ interest}{APR}$  

 $money\ on\ card=\frac{APR}{total\ interest}$ 

 $APR=\frac{total\ interest}{money\ on\ credit\ card}$ 

 $APR=\frac{money\ on\ card}{total\ interest}$  

 $money\ on\ card=\frac{total\ interest}{APR}$  

 $money\ on\ card=\frac{APR}{total\ interest}$ 

 $APR=\frac{total\ interest}{money\ on\ credit\ card}$ 

 $APR=\frac{money\ on\ card}{total\ interest}$  

$100

$200

$300

$400

.43 or 43%

.25 or 25%

.10 or 10%

1 or 100%

.43 or 43%

.25 or 25%

.10 or 10%

1 or 100%

$57

$34

$200

$1700

$57

$500

$8,000

$120,000