The plumbers want to dig a 840-meter-long pipeline, and they dug 140 meters in the first 5 days. According to this calculation, how many days will it take to dig this pipeline?
管道工人要挖一条长840米的管道，前5天挖了140米．照这样计算，挖这条管道一共需要多少天？
<gadget id="calculator">140 / 5</gadget>
<output>28</output>

<gadget id="calculator">840 / 28</gadget>
<output>30</output>

<result>30</result>