The sum of the lengths of the upper and lower bases of a trapezoid and the height are both 10 cm. What is the area of the trapezoid in square centimeters?
一个梯形上下底边长的和与高都是10厘米，这个梯形的面积是多少平方厘米．
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">10 * 5</gadget>
<output>50</output>

<result>50</result>