steel pipe is 12 meters long and is sawn into 4 sections on average. It takes 3 minutes to saw the next section, and how many minutes it will take to complete the saw.
一根钢管长12米，平均锯成4段．每锯下一段需要3分钟，锯完要花多少分钟．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<result>9</result>