What is the area of a trapezoid whose lower base is 4 decimeters and whose upper base and height are 2 decimeters?
下底是4分米，上底和高都是2分米的梯形面积是多少平方分米
<gadget id="calculator">2 + 4</gadget>
<output>6</output>

<gadget id="calculator">2 / 2</gadget>
<output>1</output>

<gadget id="calculator">6 * 1</gadget>
<output>6</output>

<result>6</result>