There is a mountain between A and B. It takes 6.5 hours for someone to go from A to B, and 7.5 hours to go from B to A. On the way back and forth, he goes uphill at a speed of 3 km/h and downhill at a speed of 4 km/h. Then, how many kilometers is the distance between A and B in the mountains?
甲、乙两地隔着一座山岭，某人从甲地到乙地用6.5小时，从乙地到甲地用7.5小时．他往返途中上山速度是3千米/时，下山速度是4千米/时．则甲、乙两地间的山岭路程有多少千米．
<gadget id="calculator">6.5 + 7.5</gadget>
<output>14</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/3) + (1/4)</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">14 / (7/12)</gadget>
<output>24</output>

<result>24</result>