pool is equipped with two water pipes A and B. The displacement of pipe B per hour is 75% of that of pipe A. First use pipe B to drain water for 5 hours, then use pipe A to drain water. As a result, the water in the pool is emptied 1 hour earlier than using pipe B only; Use pipe B to drain all the water in the pool 2 hours in advance. So how many tons of water is there in the pool?
一水池装有甲、乙两个水管．乙管每小时排水量是甲管的75%．先用乙管排水5小时后，改用甲管排水，结果比只用乙管提前1小时把水池中的水排空；如用乙管排水120吨后再改用甲管排水，则比只用乙管可提前2小时把水池中的水全部排空．那么水池原有水多少吨．
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

<gadget id="calculator">120 * 9</gadget>
<output>1_080</output>

<result>1_080</result>