A certain document needs to be printed. Xiao Li needs 3 hours to complete it independently, and Xiao Wang needs 6 hours to complete it alone. If they do it together, how many hours will it take to complete it?
某文件需要打印，小李独立做需要3小时完成，小王独立做需要6小时完成，如果他们共同做，需要多少小时完成．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/3) + (1/6)</gadget>
<output>1/2 = around 0.5</output>

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

<result>2</result>