If money is invested at r percent interest, compounded annually, the amount of the investment will double in approximately 54/r years. If Pat's parents invested $6,000 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 Pat is ready for college?
Choose the correct choice from the following answers:	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 $6,000*2=$12,000 .   Answer: $12000.
<result>C</result>
If money is invested at r percent interest, compounded annually, the amount of the investment will double in approximately 54/r years. If Pat's parents invested $6,000 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 Pat is ready for college?