There are two piles of the same number of bricks that Xiaokang and his sister have to move. It takes 10 minutes for Xiaokang to move one pile, and it takes 15 minutes for his sister to move one pile. Now how long will it take for the two to work together to move all the bricks?
有两堆同样多的砖由小康和妹妹搬完，小康搬完一堆需要10分钟，妹妹搬完一堆需要15分钟．现在两人合作搬完所有的砖块需要多长时间？
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<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">2 / (1/6)</gadget>
<output>12</output>

<result>12</result>