If money is invested at r percent interest, compounded annually, the amount of the investment will double in approximately 54/r years. If Joe's parents invested $5,000 in a long-term bond that pays 6 percent interest, compounded annually, what will be the approximate total amount of the investment 18 years later, when Joe is ready for college?	Choose one.
A) $20000	B) $15000	C) $12000	D) $10000	E) $9000
Since investment doubles in 54/r years, then for r=6 it'll double in   54/6= 
<gadget id="calculator">  54/6</gadget>
<output>9</output>
~9 years (we are not asked about the exact amount so such an approximation will do). Thus after 18 years investment will become $5,000*2=$10,000 .   Answer: $10000.
<result>D</result>
If money is invested at r percent interest, compounded annually, the amount of the investment will double in approximately 54/r years. If Joe's parents invested $5,000 in a long-term bond that pays 6 percent interest, compounded annually, what will be the approximate total amount of the investment 18 years later, when Joe is ready for college?