There is a trapezoidal cherry field, the upper bottom is 25m long, the lower bottom is 35m long, and the height is 21m. On average, each tree occupies an area of 9m**2. How many cherry trees can be planted in this field?
有一块梯形的樱桃地，上底长25m，下底长35m，高21m，平均每棵树占地9m**2，这块地能种多少棵樱桃树？
<gadget id="calculator">25 + 35</gadget>
<output>60</output>

<gadget id="calculator">21 / 2</gadget>
<output>21/2 = around 10.5</output>

<gadget id="calculator">60 * (21/2)</gadget>
<output>630</output>

<gadget id="calculator">630 / 9</gadget>
<output>70</output>

<result>70</result>