18 cows eat grass for 30 days or 20 cows eat grass for 24 days. There is a group of cows who want to eat the grass on the pasture forever, how many cows can be put at most?
18头牛吃30天草或20头牛吃24天．有一群牛要想牧场上的草永远吃不完，请问最多放几头牛？
<gadget id="calculator">18 * 30</gadget>
<output>540</output>

<gadget id="calculator">20 * 24</gadget>
<output>480</output>

<gadget id="calculator">540 - 480</gadget>
<output>60</output>

<gadget id="calculator">30 - 24</gadget>
<output>6</output>

<gadget id="calculator">60 / 6</gadget>
<output>10</output>

<result>10</result>