Xiao Ming travels from A to B, walking 6 kilometers per hour when going, and 9 kilometers per hour when returning, and it takes 5 hours to go back and forth. How many kilometers did Xiao Ming walk back and forth?
小明从甲地到乙地，去时每小时走6公里，回来时每小时走9公里，来回共用5小时．小明来回共走了多少公里．
<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>

<gadget id="calculator">2 * 18</gadget>
<output>36</output>

<result>36</result>