A piece of wood is 18 meters long, every 3 meters is sawed into a section, and it takes 4 minutes to saw each time, how many minutes does it take?
一根木头长18米，每3米锯成一段，每锯一次用4分钟，共用了多少分钟？
<gadget id="calculator">18 / 3</gadget>
<output>6</output>

<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<result>20</result>