Draw a part with a length of 4 mm on the drawing at a scale of 50:1, how many centimeters do you need to draw?
把一个长是4毫米的零件按50：1的比例尺画在图纸上，需要画多少厘米．
<gadget id="calculator">50 / 1</gadget>
<output>50</output>

<gadget id="calculator">50 / 10</gadget>
<output>5</output>

<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<result>20</result>