The distance between A and B is 500 kilometers. The passenger car and the truck depart from the two places at the same time. The passenger car travels 36 kilometers per hour. After 3 hours, the distance traveled by the two cars is exactly the whole distance (9/20). How many kilometers per hour?
甲、乙两地相距500千米，客车和货车同时从两地相对开出，客车每小时行36千米，3小时后，两车所行路程正好是全程的(9/20)，货车每小时行多少千米？
<gadget id="calculator">9 / 20</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">(9/20) / 3</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">500 * (3/20)</gadget>
<output>75</output>

<gadget id="calculator">75 - 36</gadget>
<output>39</output>

<result>39</result>