It takes 14 days for a project to be completed by B alone; if A does it on the first day, B on the second day, A on the third day, and B on the fourth day...one or two people take turns doing this, it takes 9 days to complete; if B does it on the first day, A does it on the second day, B does it on the third day, and A does it on the fourth day... One or two people take turns doing this, how many more days will it take than the last time?
一项工程，乙单独做要14天完成；如果第一天甲做，第二天乙做，第三天甲做，第四天乙做…一两人这样轮流做，需要9天完工；如果第一天乙做，第二天甲做，第三天乙做，第四天甲做…一两人这样轮流做，会比上次轮流的做法多用多少天？
<gadget id="calculator">9 + 0.5</gadget>
<output>9.5</output>

<gadget id="calculator">9.5 - 9</gadget>
<output>0.5</output>

<result>0.5</result>