The distance between A and B is 720 kilometers. It takes 20 hours for a freight train to travel from A to B, and 16 hours for a passenger train to travel from B to A. If two trains leave opposite to each other at the same time, How many hours can we meet?
甲、乙两地相距720千米，一列货车由甲地开往乙地要行20小时，一列客车由乙地开往甲地需要行驶16小时，如果两列火车同时从两地相对开出，经过几小时可以相遇？
<gadget id="calculator">720 / 20</gadget>
<output>36</output>

<gadget id="calculator">720 / 16</gadget>
<output>45</output>

<gadget id="calculator">36 + 45</gadget>
<output>81</output>

<gadget id="calculator">720 / 81</gadget>
<output>80/9 = around 8.888889</output>

<result>80/9 = around 8.888889</result>