A certain place suffered heavy rain, and the water level of the reservoir has exceeded the warning line, and there is an urgent need for flood discharge. This reservoir has two flood outlets. Only open port A, the task can be completed in 6 hours, and only open port B, the task can be completed in 9 hours. If two spillways are opened at the same time, how many hours can the task be completed?
某地遭遇暴雨，水库水位已经超过警戒线，急需泄洪．这个水库有两个泄洪口．只打开A口，6小时可以完成任务，只打开B口，9小时可以完成任务．如果两个泄洪口同时打开，几小时可以完成任务？
<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">1 / (5/18)</gadget>
<output>18/5 = around 3.6</output>

<result>18/5 = around 3.6</result>