The upper base and height of a trapezoidal piece of paper are both 3 cm, and the lower base is 1.5 times the upper base. What is the area of this trapezoidal piece of paper in square centimeters?
一张梯形纸片的上底和高都是3厘米，下底是上底的1.5倍．这张梯形纸片的面积是多少平方厘米．
<gadget id="calculator">1.5 * 3</gadget>
<output>4.5</output>

<gadget id="calculator">3 + 4.5</gadget>
<output>7.5</output>

<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">7.5 * (3/2)</gadget>
<output>11.25</output>

<result>11.25</result>