The upper base of a trapezoidal lawn is 40 meters, the lower base is 90 meters, the area is 1170 square meters, and the height is in meters.
一块梯形草地的上底是40米，下底是90米，面积是1170平方米，高是多少米．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">40 * (1/2)</gadget>
<output>20</output>

<gadget id="calculator">90 * (1/2)</gadget>
<output>45</output>

<gadget id="calculator">20 + 45</gadget>
<output>65</output>

<gadget id="calculator">1_170 / 65</gadget>
<output>18</output>

<result>18</result>