The upper base of a trapezoid is 240 cm, which is three times the height, and 60 cm shorter than the lower base. What is the area of the trapezoid in square decimeters?
一个梯形的上底是240厘米，是高的3倍，又比下底短60厘米，梯形的面积是多少平方分米．
<gadget id="calculator">240 / 10</gadget>
<output>24</output>

<gadget id="calculator">60 / 10</gadget>
<output>6</output>

<gadget id="calculator">24 + 6 + 24</gadget>
<output>54</output>

<gadget id="calculator">240 / 10 / 3 / 2</gadget>
<output>4</output>

<gadget id="calculator">54 * 4</gadget>
<output>216</output>

<result>216</result>