piece of wood is 20 meters long and it is divided into 5 equal parts. It takes 9 minutes to saw the next section. How many minutes will it take to complete the saw?
一根木头长20米，把它平均分成5段．每锯下一段需要9分钟，锯完一共要花多少分钟？
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">9 * 4</gadget>
<output>36</output>

<result>36</result>