It takes 16 hours for typist A to print a document, and 24 hours for typist B to do it alone. If typist B worked for 9 hours first, and then the two worked together, how many hours did it take to print the manuscript?
打印一份文件，甲打字员独做要16小时，乙打字员独做需24小时．如果乙打字员先做了9小时，然后两人合作，打印完这份稿件一共用了多少小时？
<gadget id="calculator">1 / 24</gadget>
<output>1/24 = around 0.041667</output>

<gadget id="calculator">(1/24) * 9</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">1 - (3/8)</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">1 / 16</gadget>
<output>1/16 = around 0.0625</output>

<gadget id="calculator">(1/16) + (1/24)</gadget>
<output>5/48 = around 0.104167</output>

<gadget id="calculator">(5/8) / (5/48)</gadget>
<output>6</output>

<gadget id="calculator">6 + 9</gadget>
<output>15</output>

<result>15</result>