It takes 20 minutes to divide a piece of wood into 5 sections on average. How many minutes will it take to divide it into 10 sections on average?
把一段木料平均分成5段需要20分钟，照这样计算，平均分成10段需要多少分钟．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

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

<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">5 * 9</gadget>
<output>45</output>

<result>45</result>