There are two water inlet pipes in the reservoir. To fill a pool of water, it takes 15 hours to turn on the A water inlet pipe alone, and it takes 10 hours to turn on the B drain pipe alone. How many hours will it take to fill half of the pool with water if two water inlets are opened at the same time?
蓄水池有两条进水管，要灌满一池水，单开A进水管需15小时，单开B排水管需10小时．如果同时开两条进水管，灌满半池水要多少小时．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/15) + (1/10)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/2) / (1/6)</gadget>
<output>3</output>

<result>3</result>