On the drawing paper with a scale of 20:1, Engineer Li draws the length of a precision instrument part with a 15cm line segment. What is the actual length of this part?
在比例尺为20：1的绘图纸上，李工程师用15cm的线段绘制一个精密仪器零件的长度，这个零件实际长度是多少？
<gadget id="calculator">20 / 1</gadget>
<output>20</output>

<gadget id="calculator">15 / 20</gadget>
<output>3/4 = around 0.75</output>

<result>3/4 = around 0.75</result>