The cross-section of a canal is trapezoidal, its mouth is 3 meters wide, its bottom is 0.4 meters shorter than its mouth, and its depth is half the width of its mouth. What is the cross-sectional area of this canal in square meters?
一条水渠的横截面是梯形，它的渠口宽是3米，渠底宽比渠口短0.4米，渠深是渠口宽的一半．这条水渠的横截面面积是多少平方米？
<gadget id="calculator">3 - 0.4</gadget>
<output>2.6</output>

<gadget id="calculator">2.6 + 3</gadget>
<output>5.6</output>

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

<gadget id="calculator">(3/2) / 2</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">5.6 * (3/4)</gadget>
<output>4.2</output>

<result>4.2</result>