There are 5 students who plant trees. In one day, they plant 20 trees in the morning and 30 trees in the afternoon. According to the daily work efficiency, how many days will it take these students to plant 200 trees?
有5个同学去种树，在一天中，上午种了20棵，下午种了30棵，照这样每天的工作效率，这些同学种200棵树需要多少天．
<gadget id="calculator">20 + 30</gadget>
<output>50</output>

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

<result>4</result>