A trapezoidal land with an upper base of 25 meters, a lower base of 45 meters and a height of 20 meters. If 7 corn seedlings are planted per square meter, how many corn seedlings are planted in this land?
一块梯形地，上底25米，下底45米，高20米．如果每平方米地种7棵玉米苗，这块地一共种玉米苗多少棵？
<gadget id="calculator">25 + 45</gadget>
<output>70</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">70 * 10 * 7</gadget>
<output>4_900</output>

<result>4_900</result>