The sum of the upper and lower bases of a trapezoid is 15 cm, the height is 2.4 cm, what is the area in square centimeters?
一个梯形上底与下底的和是15厘米，高是2.4厘米，面积是多少平方厘米．
<gadget id="calculator">2.4 / 2</gadget>
<output>1.2</output>

<gadget id="calculator">15 * 1.2</gadget>
<output>18</output>

<result>18</result>