If money is invested at r percent interest, compounded annually, the amount of the investment will double in approximately 48/r years. If Pat's parents invested $5,000 in a long-term bond that pays 8 percent interest, compounded annually, what will be the approximate total amount of the investment 18 years later, when Pat is ready for college?	Pick:
A) $20000
B) $15000
C) $12000
D) $10000
E) $9000
Since investment doubles in 48/r years, then for r=8 it'll double in   48/8= 
<gadget id="calculator">  48/8</gadget>
<output>6</output>
~6 years (we are not asked about the exact amount so such an approximation will do). Thus after 18 years investment will become $5,000*3=$15,000 .   Answer: $15000.
<result>B</result>
If money is invested at r percent interest, compounded annually, the amount of the investment will double in approximately 48/r years. If Pat's parents invested $5,000 in a long-term bond that pays 8 percent interest, compounded annually, what will be the approximate total amount of the investment 18 years later, when Pat is ready for college?