The perimeter of a right-angled trapezoid is 60 meters, the sum of the two sides is half of the sum of the two bases, and one of the sides is three times the other, find the area of the right-angled trapezoid.
一个直角梯形的周长是60米，两腰之和是两底之和的一半，且其中一腰是另一腰的3倍，求这个直角梯形的面积．
<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">60 * (1/3)</gadget>
<output>20</output>

<gadget id="calculator">60 - 20</gadget>
<output>40</output>

<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">20 * (1/4)</gadget>
<output>5</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">40 * (5/2)</gadget>
<output>100</output>

<result>100</result>