Uncle Zhang has sprayed pesticides on 540 fruit trees, 216 of which have been sprayed. The rest needs to be sprayed within 3 days. How many trees need to be sprayed per day on average to complete the project on schedule?
张伯伯给540棵果树喷洒农药，已经喷了216棵．剩下的要在3天内喷完，平均每天要喷多少棵才能按期完工？
<gadget id="calculator">540 - 216</gadget>
<output>324</output>

<gadget id="calculator">324 / 3</gadget>
<output>108</output>

<result>108</result>