The line segment AB=5, extend AB to C, so that BC=2AB, if D is the midpoint of AB, what is the length of DC? (expressed as a decimal)
线段AB=5，延长AB到C，使BC=2AB，若D为AB的中点，则DC的长是多少．(用小数表示)
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">10 + (5/2)</gadget>
<output>25/2 = around 12.5</output>

<result>25/2 = around 12.5</result>