The area of an approximately trapezoidal lawn is 640 square meters. It is known that its upper base is 26 meters and its lower base is 38 meters. How many meters is it high?
一块近似梯形的草地面积是640平方米．已知它的上底是26米，下底是38米．它的高是多少米？
<gadget id="calculator">26 + 38</gadget>
<output>64</output>

<gadget id="calculator">2 / 64</gadget>
<output>1/32 = around 0.03125</output>

<gadget id="calculator">640 * (1/32)</gadget>
<output>20</output>

<result>20</result>