To fill a pool, it takes 8 hours to open only tube A, 10 hours to open only tube B, and 15 hours to open only tube C. At the beginning, only pipes A and B were opened, and pipes A and B were turned off halfway, and then pipe C was opened. It took 10 hours and 15 minutes to fill the pool, so how long did pipe C remain open?
灌满一个水池，只打开A管要8小时，只打开B管要10小时，只打开C管要15小时．开始时只打开A管和B管，中途关掉A管和B管，然后打开C管，前后共用了10小时15分钟灌满了水池，那么，C管打开了多少时间？
<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/8) * 10.25</gadget>
<output>1.28125</output>

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

<gadget id="calculator">(1/10) * 10.25</gadget>
<output>1.025</output>

<gadget id="calculator">1.025 - 1</gadget>
<output>0.025</output>

<gadget id="calculator">1.28125 + 0.025</gadget>
<output>1.30625</output>

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

<gadget id="calculator">(1/10) - (1/15)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/8) + (1/30)</gadget>
<output>19/120 = around 0.158333</output>

<gadget id="calculator">1.30625 / (19/120)</gadget>
<output>8.25</output>

<result>8.25</result>