The sum of the upper and lower bases of a right-angled trapezoid is 20 cm, and the two sides are 6 cm and 10 cm respectively. What is its area in square centimeters?
一个直角梯形上下底的和是20厘米，两条腰分别是6厘米和10厘米，它的面积是多少平方厘米．
<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">20 * 3</gadget>
<output>60</output>

<result>60</result>