Cut a steel pipe into 6 sections, each section takes 3 minutes, how many minutes will it take in total?
把一根钢管截成6段，每截一次用3分钟，一共要用多少分钟．
<gadget id="calculator">6 - 1</gadget>
<output>5</output>

<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<result>15</result>