Each minute on a clock or watch is 6°, as you divide 360° by 60 minutes. As you can see, 32 minutes elapsed during the class. Therefore we just multiply.
If the interest per quarter is 4% (but interest is only compounded annually), then it will take (72 / 4) = 18 quarters or 4.5 years to double the principal. If the population of a nation increases at the rate of 1% per month, it will double in 72 months, or six years.
