Michelle paid $72 on a $600 loan for 2.5 years. what was the interest rate?

The first decimal place has the digit 0

the second decimal place has the digit 7

the third decimal place has the digit either 1 or 2.

this depends on the forth one, if it was 5 or higher, the third digit would be 2
since the fourth digit is 3, which is lower than 5, we don't have to change the third digit : it remains a "1"

so the answer is 0.071