The upper base of the trapezoid is 1.5 decimeters, the lower base is 2.5 decimeters, and the height is 3.5 decimeters. What is the area in square decimeters?
梯形的上底是1.5分米，下底是2.5分米，高是3.5分米，面积是多少平方分米
<gadget id="calculator">1.5 + 2.5</gadget>
<output>4</output>

<gadget id="calculator">3.5 / 2</gadget>
<output>1.75</output>

<gadget id="calculator">4 * 1.75</gadget>
<output>7</output>

<result>7</result>