A project can be completed by team A alone in 30 days and team B alone in 20 days. After 6 days of cooperation between teams A and B, how much is left unfinished?
一项工程，甲队单独做30天完成，乙队单独做20天完成．甲、乙两队合做6天后，还剩下多少没有完成？
<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/30) + (1/20)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/12) * 6</gadget>
<output>1/2 = around 0.5</output>

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

<result>1/2 = around 0.5</result>