There is a trapezoidal plank, the upper base is 0.6 meters longer than the lower base, the upper base is 1.8 meters, and the height is 0.9 meters less than the lower base. What is the area of this wooden board?
有一块梯形木板，上底比下底多0.6米，上底是1.8米，高比下底少0.9米，这块木板的面积是多少．
<gadget id="calculator">1.8 - 0.6</gadget>
<output>1.2</output>

<gadget id="calculator">1.8 + 1.2</gadget>
<output>3</output>

<gadget id="calculator">1.2 - 0.9</gadget>
<output>0.3</output>

<gadget id="calculator">0.3 / 2</gadget>
<output>0.15</output>

<gadget id="calculator">3 * 0.15</gadget>
<output>0.45</output>

<result>0.45</result>