The length of the railway between A and B is 1260 kilometers, and it takes 10 hours for the express train to complete the journey, and 15 hours for the slow train to complete the journey. Now the express train and the local train leave opposite directions at the same time, how many hours will they meet?
甲乙两地铁路长1260千米，快车行完全程要10小时，慢车行完全程要15小时．现在快车和慢车同时从两地相向开出，几小时相遇？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/10) + (1/15)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / (1/6)</gadget>
<output>6</output>

<result>6</result>