The cross-sectional area of a canal is trapezoidal, the area is 9 square meters, the upper bottom is 5.5 decimeters, and the lower bottom is 3.5 decimeters. How deep is this canal in meters?
一条水渠的横截面积是梯形，面积是9平方米，上底是5.5分米，下底是3.5分米，这条水渠深多少米．
<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">9 * (2/9)</gadget>
<output>2</output>

<result>2</result>