There is a trapezoidal orchard with an upper base of 30 meters, a lower base of 42 meters and a height of 20 meters. Pear trees are planted in the orchard. If each pear tree covers an area of 12 square meters, how many pear trees can be planted?
有一块近似梯形的果园，上底30米，下底42米，高20米，在果园里栽上梨树，如果每棵梨树占地12平方米，大约可以栽多少棵？
<gadget id="calculator">30 + 42</gadget>
<output>72</output>

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

<gadget id="calculator">72 * 10</gadget>
<output>720</output>

<gadget id="calculator">720 / 12</gadget>
<output>60</output>

<result>60</result>