Xiao Wang crossed the top of the mountain from place A and descended to place B. He goes uphill at 5km per hour and downhill at 8km per hour. He goes from A to B and immediately returns to A by the same route. It takes 8.4 hours. What is the distance between A and B?
小王从甲地越过山顶下山到达乙地．他上山每小时行5km，下山每小时行8km，从甲地到乙地后立即按原路返回甲地，共用8.4h，甲乙两地间的路程是多少？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">(1/5) + (1/8)</gadget>
<output>13/40 = around 0.325</output>

<gadget id="calculator">8.4 / (13/40)</gadget>
<output>25.846154</output>

<result>25.846154</result>