The scale of a drawing of a precision part is 20:1, and the length of a certain part measured on the drawing is 3cm, so what is the actual length of this part?
一张精密零件图纸的比例尺是20：1，在图上量的某零部件长3cm，那么这个零件的实际长度是多少？
<gadget id="calculator">20 / 1</gadget>
<output>20</output>

<gadget id="calculator">10 / 20</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3 * (1/2)</gadget>
<output>3/2 = around 1.5</output>

<result>3/2 = around 1.5</result>