The cistern has an inlet pipe and a drain pipe. It takes 3 hours for the drain pipe to empty the pool of water, and it takes 4 hours for the inlet pipe to fill the pool with water. Now there is half a pool of water, if the water is drained, inflowed, drained, inflowed in the order of 1 hour each, how long will it take at least to drain the water in the pool?
蓄水池有一条进水管和一条排水管，排水管要3小时排光一池水，进水管则要4小时才灌满一池水．现在有半池水，如果按排水、进水、排水、进水..的顺序轮流各开1小时，问最少需要多久才把水池的水排完？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(1/2) - (1/3)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) - (1/3)</gadget>
<output>-1/12 = around -0.083333</output>

<gadget id="calculator">(1/6) + (-1/12) + (1/4)</gadget>
<output>1/3 = around 0.333333</output>

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

<gadget id="calculator">1 + 1 + 1 + 1 + 1</gadget>
<output>5</output>

<result>5</result>