The scale of a drawing is 20:1, a precision part is 2.5mm long, how many centimeters should be drawn on this drawing.
一张图纸的比例尺是20﹕1，一个精密零件长2.5毫米，在这张图纸上要画多少厘米．
<gadget id="calculator">20 / 1</gadget>
<output>20</output>

<gadget id="calculator">20 / 10</gadget>
<output>2</output>

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

<result>5</result>