Simon and grandma go for a walk on the playground together. It takes 10 minutes for Simon to walk around, and 15 minutes for grandma to walk around. If they start at the same place at the same time and walk opposite each other, how many minutes later will they meet?
赛门和奶奶一起去操场散步，赛门走一圈要10分钟，奶奶走一圈要15分钟，如果两人同时同地出发，相背而行，多少分钟后相遇？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

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

<gadget id="calculator">(1/10) + (1/15)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / (1/6)</gadget>
<output>6</output>

<result>6</result>