The capacity of a pool is 1200 liters. It has two water inlet pipes A and B and one outlet pipe C. It is known that it takes 9 hours and 10 hours for the two pipes A and B to fill the empty pool respectively. Now there is a part of water in the pool , If pipes A and C are opened at the same time, the water can be drained in 3 hours. If the three water pipes A, B, and C are opened at the same time, the water can be drained in 5 hours. How many liters of water is there in the pool?
一个水池的容量是1200升，它有A、B两个进水管和一个出水管C，已知A、B两管单独注满空水池分别要9小时和10小时，现在水池中存有一部分水，如果同时打开A管和C管，则3小时可把水放完，如果同时打开A、B、C三个水管，则5小时可以把水放完，问水池原来有水多少升？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/3) - (1/5)</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">1_200 / 10 / (2/15)</gadget>
<output>900</output>

<result>900</result>