On a drawing with a scale of 30:1, the length of a part on the drawing is 12 cm, what is its actual length?
在一幅比例尺是30：1的图纸上，一个零件的图上长度是12厘米，它的实际长度是多少．
<gadget id="calculator">30 / 1</gadget>
<output>30</output>

<gadget id="calculator">12 / 30</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>