It takes 5 minutes to cut a 3-meter-long piece of wood into 4 small sections. How many minutes did it take to saw all of them?
把3米长的木料锯成4小段，每锯下一小段需5分钟．全部锯完需多少分钟？
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

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

<result>15</result>