The two water inlet pipes A and B are opened at the same time, 40% of the pool can be filled in 4 hours, then pipe A is opened alone for 5 hours, and pipe B is opened for 7.4 hours to fill the pool. Question: If pipe B is opened alone, how long will it take Can the pool be filled?
甲乙两根进水管同时打开，4小时可注满水池的40%，接着甲管单独开5小时，再由乙管单独开7.4小时，方才注满水池，问：如果独开乙管，多少时间可将水池注满？
<gadget id="calculator">7.4 - 5</gadget>
<output>2.4</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) / 4</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) * 5</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(2/5) + (1/2)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">2.4 / (1/10)</gadget>
<output>24</output>

<result>24</result>