Two identical trapezoids are put together to form a parallelogram. The area of this parallelogram is 280cm and the height is 35cm. What is the sum of the upper and lower bases of each trapezoid in cm?
两个完全一样的梯形拼成一个平行四边形，这个平行四边形的面积是280cm，高是35cm，每个梯形的上底、下底之和是多少cm．
<gadget id="calculator">280 / 2</gadget>
<output>140</output>

<gadget id="calculator">2 / 35</gadget>
<output>2/35 = around 0.057143</output>

<gadget id="calculator">140 * (2/35)</gadget>
<output>8</output>

<result>8</result>