Two water pipes discharge water to the pool. The first water pipe discharges 2.5 tons of water per hour. After 4 tons, the second water pipe starts to discharge. The second water pipe discharges 3.3 tons of water per hour. After the second water pipe is discharged for a few hours, The tonnage of water released by the two water pipes is equal?
两根水管向水池放水，第一根水管每小时放水2.5吨，放了4吨后第二根水管才开始放，第二根水管每小时放水3.3吨，第二根水管放了几小时后，两根水管放水的吨数相等？
<gadget id="calculator">3.3 - 2.5</gadget>
<output>0.8</output>

<gadget id="calculator">4 / 0.8</gadget>
<output>5</output>

<result>5</result>