Exploration: It takes 20 minutes to saw a piece of wood into 9 sections, how many minutes will it take to saw 18 sections at the same speed.
探索：把一根木料锯成9段要20分钟，同样速度锯成18段要多少分钟．
<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<gadget id="calculator">20 / 8</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">18 - 1</gadget>
<output>17</output>

<gadget id="calculator">(5/2) * 17</gadget>
<output>85/2 = around 42.5</output>

<result>85/2 = around 42.5</result>