It takes 6 days for Team A to complete a project alone, and 4 days for Team B to complete it alone. Now Team A will finish (1/6) first, and then the two teams will work together. How many days will it take to finish?
一项工程，甲队单独完成要6天，乙队单独完成要4天．现先由甲队做完(1/6)后，再两队合做完成，还要几天才能做完？
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 - (1/6)</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/6) + (1/4)</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">(5/6) / (5/12)</gadget>
<output>2</output>

<result>2</result>