On a drawing with a scale of 4:1, the measured length of the part is 20 cm. What is the actual length of this part?
在一副比例尺为4：1的图纸上，量得零件的长是20厘米．这个零件的实际长度是多少？
<gadget id="calculator">4 / 1</gadget>
<output>4</output>

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

<result>5</result>