The sum of the upper and lower bases of a trapezoid is 14.4 decimeters, which is three times the height. What is the area of the trapezoid?
一个梯形的上、下底的和为14.4分米，是高的3倍，这个梯形的面积是多少．
<gadget id="calculator">14.4 / 3</gadget>
<output>4.8</output>

<gadget id="calculator">4.8 / 2</gadget>
<output>2.4</output>

<gadget id="calculator">14.4 * 2.4</gadget>
<output>34.56</output>

<result>34.56</result>