The upper base of a trapezoid is 8 cm, the lower base is 12 cm, and the height is 2.4 cm. What is its area in square centimeters?
一个梯形的上底是8厘米，下底是12厘米，高是2.4厘米，它的面积是多少平方厘米．
<gadget id="calculator">8 + 12</gadget>
<output>20</output>

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

<gadget id="calculator">20 * 1.2</gadget>
<output>24</output>

<result>24</result>