The distance between A and B is 500 kilometers. A passenger car and a truck leave opposite to each other at the same time. The speed of the passenger car is 36 km/h. After 3 hours, the distance traveled by the two vehicles is exactly 45% of the whole journey. What is the speed of the truck?
甲、乙两地相距500千米，客车和货车同时从两地相对开出，客车的速度是36千米/时．3小进后，两车所行的路程正好是全程的45%，货车的速度是多少？
<gadget id="calculator">45 / 100</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">500 * (9/20)</gadget>
<output>225</output>

<gadget id="calculator">36 * 3</gadget>
<output>108</output>

<gadget id="calculator">225 - 108</gadget>
<output>117</output>

<gadget id="calculator">117 / 3</gadget>
<output>39</output>

<result>39</result>