The fourth grade students want to plant 740 trees, and 540 have been planted. How many hours will it take to plant 50 trees per hour?
四年级同学要种740棵树，已经种下了540棵．如果每小时种50棵树，还需几小时种完？
<gadget id="calculator">740 - 540</gadget>
<output>200</output>

<gadget id="calculator">200 / 50</gadget>
<output>4</output>

<result>4</result>