A pool is equipped with an inlet pipe and an outlet pipe. The whole pool can be filled in 5 hours with the water inlet pipe alone, and a pool of water can be drained in 6 hours with the water outlet pipe alone. Now that the water inlet and outlet pipes are opened at the same time, how many hours can the pool be filled?
一水池装有进、出水管各一根，单开进水管5小时注满全池，单开出水管6小时可放完一池水．现在进、出水管同时开，几小时可灌满水池？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/5) - (1/6)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / (1/30)</gadget>
<output>30</output>

<result>30</result>