There is a piece of wood that is 4 meters long, and it needs to be sawed into 8 sections, and it takes 3 minutes to saw each section. How many minutes were sawed.
有一根木材长4米，要把它锯成8段，每锯一段要用3分钟．共锯了多少分钟．
<gadget id="calculator">8 - 1</gadget>
<output>7</output>

<gadget id="calculator">7 * 3</gadget>
<output>21</output>

<result>21</result>