The upper base of the trapezoid is 2 cm, the lower base is 8 cm, and the height is 4.5 cm. What is the area of the trapezoid?
梯形的上底是2厘米，下底是8厘米，高是4.5厘米梯形的面积是多少．
<gadget id="calculator">2 + 8</gadget>
<output>10</output>

<gadget id="calculator">4.5 / 2</gadget>
<output>2.25</output>

<gadget id="calculator">10 * 2.25</gadget>
<output>22.5</output>

<result>22.5</result>