The diameter of a part measured on a drawing with a scale of 20:1 is 4 cm. What is the actual length of the part in millimeters?
在比例尺是20：1的图纸上量得一个零件的直径是4厘米，这个零件直径的实际长度是多少毫米．
<gadget id="calculator">20 / 1</gadget>
<output>20</output>

<gadget id="calculator">4 / 20</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) * 10</gadget>
<output>2</output>

<result>2</result>