An investment of $2000 was made in a certain account and earned interest that was compounded annually. The annual interest rate was fixed for the duration of the investment, and after 12 years the $1000 increased to $8000 by earning interest. In how many years after the initial investment was made the $1000 have increased to $16000 by earning interest at that rate?  Choose the correct choice from the following.
A) 18	B) 12	C) 20	D) 24	E) 30
In 12 years the investment quadrupled (from $2,000 to $8,000).   Thus, at the same rate compounded annually, it would need additional   12/2= 
<gadget id="calculator">  12/2</gadget>
<output>6</output>
6 years to double (from $8,000 to $16,000).   Therefore, 12+6=18 years are needed $2,000 to increase to $16,000.   18nswer: 18.
<result>A</result>
An investment of $2000 was made in a certain account and earned interest that was compounded annually. The annual interest rate was fixed for the duration of the investment, and after 12 years the $1000 increased to $8000 by earning interest. In how many years after the initial investment was made the $1000 have increased to $16000 by earning interest at that rate?