Two passenger and freight cars depart from stations A and B which are 780 kilometers apart at the same time. After 5 decimals, the distance between the two cars is still 30 kilometers. It is known that the passenger car travels 81 kilometers per hour, and how many kilometers per hour does the truck travel ?
客货两车分别从相距780千米的A、B两站同时相对开出，经过5小数后两车还相距30千米，已知客车每小时行81千米，货车每小时行多少千米？
<gadget id="calculator">780 - 30</gadget>
<output>750</output>

<gadget id="calculator">750 / 5</gadget>
<output>150</output>

<gadget id="calculator">150 - 81</gadget>
<output>69</output>

<result>69</result>