Xiao Wang goes up the mountain from A to B, crosses the top of the mountain and descends to B. He travels 3 km per hour up the mountain and 5 km per hour down the mountain. From A to B, he immediately returns to A by the same route and takes 6.4 hours. The distance between A and B is How many kilometers?
小王从甲地上山越过山顶下山到达乙地，他上山每小时行3km，下山每小时行5km，从甲地到乙地后立即按原路返回甲地共用时6.4h，甲乙两地间的路程是多少千米？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/3) + (1/5)</gadget>
<output>8/15 = around 0.533333</output>

<gadget id="calculator">6.4 / (8/15)</gadget>
<output>12</output>

<result>12</result>