The sum of the two bases of the trapezoid is 45 meters and the height is 12 meters. What is its area?
梯形的两底之和是45米，高12米，它的面积是多少．
<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">45 * 6</gadget>
<output>270</output>

<result>270</result>