The upper base of a trapezoid is 5cm, the lower base is 4cm, and the height is 2.4cm. What is the area of the trapezoid?
一个梯形的上底是5cm，下底是4cm，高是2.4cm，这个梯形的面积是多少．
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">2.4 / 2</gadget>
<output>1.2</output>

<gadget id="calculator">9 * 1.2</gadget>
<output>10.8</output>

<result>10.8</result>