If the interest earned by a cd is compounded quarterly and the money invested is doubled after a certain time. So, we are given an interest rate, an initial amount and a final amount.
First, convert the interest rate to per yer compounded yearly. Next, use this formula to solve for the number of years to double the amount:
The sum of two irrational numbers, in some cases Will be irrational. However, if the rational parts of the numbers have a 0 sum (cancel each other out), the sum will be rational.