Xiaohua and Xiaoqiang are walking toward each other at the same speed along a small road next to the railway. A train passes by them, and it takes 18 seconds and 15 seconds respectively. So how many times the speed of this train is the speed of the two children?
小华和小强沿铁路旁的一条小路以同样的速度相向而行，一列火车从他们两人身旁经过，分别用时18秒和15秒．那么这列火车的速度是这两个小朋友的速度的多少倍？
<gadget id="calculator">1 / 18</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/18) + (1/15)</gadget>
<output>11/90 = around 0.122222</output>

<gadget id="calculator">(11/90) / 2</gadget>
<output>11/180 = around 0.061111</output>

<gadget id="calculator">(1/15) - (11/180)</gadget>
<output>1/180 = around 0.005556</output>

<gadget id="calculator">(11/90) / 2 / (1/180)</gadget>
<output>11</output>

<result>11</result>