There is a trapezoid with a height of 15 decimeters, the lower base is 28 decimeters, and the lower base is 4 times the upper base. What is the area of this reminder in square decimeters?
有一个高为15分米的梯形，下底是28分米，下底是上底的4倍，这个提醒的面积是多少平方分米？
<gadget id="calculator">28 / 4</gadget>
<output>7</output>

<gadget id="calculator">7 + 28</gadget>
<output>35</output>

<gadget id="calculator">15 / 2</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">35 * (15/2)</gadget>
<output>525/2 = around 262.5</output>

<result>525/2 = around 262.5</result>