To type a manuscript, there are two typists, A and B, but only one computer. A plays singles in 10 hours, and B plays singles in 12 hours. Now the two take turns to type, A for half an hour, and then B for half an hour... Taking turns in this way, how many hours did it take B to finish typing this manuscript?
打一份稿件，有甲乙两打字员，但只有一电脑．甲单打10小时打完，乙单打12小时打完．现在两人轮流打，甲打半小时，然后乙打半小时…如此轮流，打完这份稿件乙共用了多少小时．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 12</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/10) + (1/12)</gadget>
<output>11/60 = around 0.183333</output>

<gadget id="calculator">5 / 11</gadget>
<output>5/11 = around 0.454545</output>

<gadget id="calculator">(11/60) * (5/11)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/10) * (1/2)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/12) - (1/20)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/30) / (1/12)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) + 5</gadget>
<output>27/5 = around 5.4</output>

<result>27/5 = around 5.4</result>