The upper base of the trapezoid is 4 decimeters, the lower base is 9 decimeters, and the area is 65 square decimeters. Find the height of the trapezoid.
梯形的上底是4分米，下底是9分米，面积65平方分米．求梯形的高．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">4 * (1/2)</gadget>
<output>2</output>

<gadget id="calculator">9 * (1/2)</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">2 + (9/2)</gadget>
<output>13/2 = around 6.5</output>

<gadget id="calculator">65 / (13/2)</gadget>
<output>10</output>

<result>10</result>