The scale of a picture is 20:1, and the distance of 4cm is measured on this picture, how many cm is it actually
一幅图的比例尺是20：1，在这幅图上量得4cm的距离，实际是多少cm
<gadget id="calculator">20 / 1</gadget>
<output>20</output>

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

<result>1/5 = around 0.2</result>