A piece of wood has to be sawn into 4 pieces. It takes 5 minutes to saw each time, how many minutes will it take to complete the saw.
一根木头要把它锯成4段．每锯一次需要5分钟，锯完一共需要多少分钟．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

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

<result>15</result>