A fish pond is trapezoidal, the bottom is 100m long, the top is 80m long, and the height is 10m. What is the area of this fish pond?
一个鱼塘是梯形的，下底长100m，上底长80m，高10m．这个鱼塘的面积是多少？
<gadget id="calculator">80 + 100</gadget>
<output>180</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">180 * 5</gadget>
<output>900</output>

<result>900</result>