Two trains depart opposite from each other at the same time. One train takes 10 hours to complete the journey, and the other train takes 8 hours to complete the journey. After how many hours did the two cars meet?
两列火车从两城同时相对开出．一列火车行完全程要10小时，另一列火车行完全程要8小时．经过几小时两车相遇？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/10) + (1/8)</gadget>
<output>9/40 = around 0.225</output>

<gadget id="calculator">1 / (9/40)</gadget>
<output>40/9 = around 4.444444</output>

<result>40/9 = around 4.444444</result>