A cistern without a cover has a drainage hole on its side at (1/3) height and (2/3) height, and their drainage speeds are the same and remain constant. Now fill the water tank from above at a certain speed. If you open A and close B, the water tank can be filled in 35 minutes; if you open B and close A, you can fill the water tank in 40 minutes; if both holes are open, how many minutes will it take? Fill up the water tank?
一个没有盖的水箱，在其侧面(1/3)高和(2/3)高的位置各有一个排水孔，它们排水的速度相同且保持不变．现在以一定的速度从上面给水箱注水，如果打开A关闭B，35分钟可以将水箱注满；如果打开B关闭A，40分钟可以将水箱注满；如果两个孔都打开，需要多少分钟才能将水箱注满？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">35 - 5</gadget>
<output>30</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/3) / (1/30)</gadget>
<output>10</output>

<gadget id="calculator">(1/30) * 35</gadget>
<output>7/6 = around 1.166667</output>

<gadget id="calculator">(7/6) - 1</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">30 * (2/3)</gadget>
<output>20</output>

<gadget id="calculator">35 - 20</gadget>
<output>15</output>

<gadget id="calculator">(1/6) / 15</gadget>
<output>1/90 = around 0.011111</output>

<gadget id="calculator">(1/30) - (1/90)</gadget>
<output>1/45 = around 0.022222</output>

<gadget id="calculator">(1/3) / (1/45)</gadget>
<output>15</output>

<gadget id="calculator">(1/90) * 2</gadget>
<output>1/45 = around 0.022222</output>

<gadget id="calculator">(1/30) - (1/45)</gadget>
<output>1/90 = around 0.011111</output>

<gadget id="calculator">(1/3) / (1/90)</gadget>
<output>30</output>

<gadget id="calculator">10 + 15 + 30</gadget>
<output>55</output>

<result>55</result>