A piece of wood is 21 meters long, and it is sawn into a section 3 meters long. It takes 6 minutes to saw each section, how many minutes are used.
一根木料长21米，把它锯成3米长的一段．每锯一段要用6分钟，共用多少分钟．
<gadget id="calculator">21 / 3</gadget>
<output>7</output>

<gadget id="calculator">7 - 1</gadget>
<output>6</output>

<gadget id="calculator">6 * 6</gadget>
<output>36</output>

<result>36</result>