Interest rate: You are in a desperate need of cash and turn to your uncle, who has offered to lend you some money. You decide to borrow $1,300 and agree to pay back $1,500 in two years. Alternatively, you could borrow from your bank that is charging 6.5 percent interest annually. Should you go with your uncle or the bank?

Number of periods: You invest $150 in a mutual fund today that pays 9 percent interest annually. How long will it take to double your money?