It takes 20 minutes to saw a piece of wood into 6 sections. According to this calculation, how many minutes will it take to saw it into 4 sections?
把一根木料锯成6段要20分钟，照这样计算，锯成4段要多少分钟．
<gadget id="calculator">6 - 1</gadget>
<output>5</output>

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

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<result>12</result>