A cistern holds one eighteenth of its capacity in water. The two water injection pipes inject water into the pool at the same time. When the water volume of the pool reaches two-ninths, the first water injection pipe starts to inject water into the pool alone. It takes 81 minutes, and the amount of water injected is equal to the water injected by the second water injection pipe into the pool. water volume Then the second water injection pipe injects water into the pool alone for 49 minutes. At this time, the total amount of water injected into the pool by the two water injection pipes is the same. After that, the two water injection pipes continue to fill the pool. Then how many minutes do the two water injection pipes need to inject water together to fill the pool.
某个水池存有其容量的十八分之一的水．两条注水管同时向水池注水，当水池的水量达到九分之二时，第一条注水管开始单独向水池注水，用时81分钟，所注入的水量等于第二条注水管已注入水池内的水量．然后第二条注水管单独向水池注水49分钟，此时，两条注水管注入水池的总水量相同．之后，两条注水管都继续向水池注水．那么两条注水管还需要一起注水分钟多少，方能将水池注满．
<gadget id="calculator">9 * 7</gadget>
<output>63</output>

<gadget id="calculator">11 / 18</gadget>
<output>11/18 = around 0.611111</output>

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

<gadget id="calculator">(11/18) / (1/6)</gadget>
<output>11/3 = around 3.666667</output>

<gadget id="calculator">63 * (11/3)</gadget>
<output>231</output>

<result>231</result>