Tanner has invested $500 for college. what rate of return must tanner earn for his investment to double in six years

This is answered using the Rule of 72. This is the easiest way to know how long an investment will take to double, given a fixed annual rate of interest

The rule of 72 is the period to double multiplied by the interest rate equal 72.

So to do this: Just divide 72 and 6. 72/6 = 12% would be the rate of return