A trapezoidal orchard has an upper base of 80 meters, a lower base of 100 meters, and a height of 50 meters. If one fruit tree is planted every 9 square meters, how many fruit trees can be planted in this orchard?
一个梯形果园，上底是80米，下底是100米，高是50米．如果每9平方米栽一棵果树，这个果园一共能栽多少棵果树？
<gadget id="calculator">80 + 100</gadget>
<output>180</output>

<gadget id="calculator">50 / 2 / 9</gadget>
<output>25/9 = around 2.777778</output>

<gadget id="calculator">180 * (25/9)</gadget>
<output>500</output>

<result>500</result>