This problem illustrates a deceptive way of quoting interest rates called add-on interest. Imagine that you see an advertisement for Crazy Judys Stereo City that reads something like this: $1,000 Instant Credit! 17.9% Simple Interest! Three Years to Pay! Low, Low Monthly Payments! Youre not exactly sure what all this means and somebody has spilled ink over the APR on the loan contract, so you ask the manager for clarification.

Judy explains that if you borrow $1,000 for three years at 17.9 percent interest, in three years you will owe:

$1,000 1.179³ = $1,000 1.63886 = $1,638.86

Now, Judy recognizes that coming up with $1,638.86 all at once might be a strain, so she lets you make low, low monthly payments of $1,638.86 / 36 = $45.52 per month, even though this is extra bookkeeping work for her.

What is the APR on this loan?