A water reservoir is equipped with three water inlet pools A, B, and C. The two pipes A and B are opened at the same time, and the whole pool is filled in 45 minutes; B and C are opened in 60 minutes to fill up, and A and C are opened in 90 minutes to fill up. , three tubes open together, how many hours will it take?
一个蓄水池装有甲、乙、丙三个进水池，同时开放甲、乙两管，45分钟注满全池，同时开放乙、丙60分钟注满，同时开放甲、丙90分钟注满，三管一起开放，需要多少小时？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<result>2/3 = around 0.666667</result>