A train of passenger cars and a train of freight trains depart from places A and B at the same time. After 3 hours, the distance between the two cars is still 135km. After driving for another 3 hours, the distance between the two cars is 135km. The speed ratio of the passenger car and the freight car is 5 : 4. How many kilometers does the bus travel per hour?
一列客车和一列货车同时从甲、乙两地相向开出，3小时后两车之间还相距135km，接着又行驶了3小时，两车之间又相距135km，客车和货车的速度比是5：4，客车每小时行多少km？
<gadget id="calculator">135 + 135</gadget>
<output>270</output>

<gadget id="calculator">270 / 3</gadget>
<output>90</output>

<gadget id="calculator">5 / 9</gadget>
<output>5/9 = around 0.555556</output>

<gadget id="calculator">90 * (5/9)</gadget>
<output>50</output>

<result>50</result>