Dave has been introduced to a new phone service. They charge a monthly fee of $5 and each phone call made out of country is $8. How much phone calls did Dave made out of country if his bill this month was 37?
Inverse variation means that when the frequency goes up by a factor of 576/256 = 9/4, the length of the string goes down by a factor that is the inverse of that, 4/9.
