A pool is equipped with water inlet and outlet pipes, the empty pool can be filled in 3 hours with the water inlet alone, and the full pool can be drained in 5 hours with the water outlet alone. Open the water inlet and outlet pipes at the same time, turn off the water outlet pipes after 2 hours, how many hours will it take to fill the whole pool?
一个水池装有进水管和出水管，单开进水管3小时可将空池注满；单开出水管5小时可将满池水放完．同时打开进水管和出水管，2小时后关掉出水管，还要几小时可以将全池注满？
<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">(2/15) * 2</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">1 - (4/15)</gadget>
<output>11/15 = around 0.733333</output>

<gadget id="calculator">(11/15) / (1/3)</gadget>
<output>11/5 = around 2.2</output>

<result>11/5 = around 2.2</result>