tractor plows the land at the same speed. It takes 4.5 hours to plow the land on the first day, and 8 hours to plow the land on the second day. The plowing area on the first day is 420 square meters less than that on the second day. How many square meters does this tractor cultivate per hour?
一台拖拉机用同样的速度耕地，第一天耕地4.5小时，第二天耕地8小时，第一天比第二天少耕地420平方米．这台拖拉机每小时耕地多少平方米？
<gadget id="calculator">8 - 4.5</gadget>
<output>3.5</output>

<gadget id="calculator">420 / 3.5</gadget>
<output>120</output>

<result>120</result>