The upper base of a trapezoid is 10 cm, the lower base is 20 cm, and the area is 300 cm2. What is the height of the trapezoid in cm?
一个梯形的上底是10厘米，下底是20厘米，面积是300平方厘米，这个梯形的高是多少厘米．
<gadget id="calculator">10 + 20</gadget>
<output>30</output>

<gadget id="calculator">2 / 30</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">300 * (1/15)</gadget>
<output>20</output>

<result>20</result>