To plant 818 poplars, 218 have been planted. The rest will be planted in 15 days. How many trees are planted per day on average?
要种818棵杨树，已经种了218棵．剩下的要15天种完．平均每天要种多少棵？
<gadget id="calculator">818 - 218</gadget>
<output>600</output>

<gadget id="calculator">600 / 15</gadget>
<output>40</output>

<result>40</result>