Xiao Ming goes from A to B, walking 6 kilometers per hour when going, and 9 kilometers per hour when returning. It took 5 hours to go back and forth, how many kilometers are there between places A and B?
小明从甲地去乙地，去时每小时走6千米，回时每小时走9千米．来回共用了5小时，甲乙两地多少千米．
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 9</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/6) + (1/9)</gadget>
<output>5/18 = around 0.277778</output>

<gadget id="calculator">5 / (5/18)</gadget>
<output>18</output>

<result>18</result>