4 swallows eat 540 pests in 4.5 days, how many pests does each swallow eat per day?
4只燕子4.5天吃害虫540只，平均每只燕子每天吃害虫多少只？
<gadget id="calculator">540 / 4.5 / 4</gadget>
<output>30</output>

<result>30</result>