A piece of work is completed in 7 hours by A and B in cooperation, and 16 hours by B alone. After A has worked for 3 hours, B has worked for 4 hours. What percentage of the work has been completed?
一件工作，甲乙合作7小时完成，乙独做16小时完成，甲工作3小时后，乙工作4小时，共完成这件工作的几分之几？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

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

<gadget id="calculator">(1/7) - (1/16)</gadget>
<output>9/112 = around 0.080357</output>

<gadget id="calculator">(9/112) * 3</gadget>
<output>27/112 = around 0.241071</output>

<gadget id="calculator">(1/16) * 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(27/112) + (1/4)</gadget>
<output>55/112 = around 0.491071</output>

<result>55/112 = around 0.491071</result>