The sum of the upper and lower bases of a right-angled trapezoid is 40 cm, and the length of the shorter side is 16 cm. What is the area in square centimeters?
一个直角梯形上下底的和是40厘米，较短的腰长16厘米，面积是多少平方厘米．
<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<gadget id="calculator">40 * 8</gadget>
<output>320</output>

<result>320</result>