One job is done alone, A takes 6 hours and B takes 4 hours. After A has done (1/3), how many hours will it take for the two to finish it together?
一件工作，单独完成，甲要6小时，乙要4小时．甲做了(1/3)后，两人合做，还要几小时才能做完？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 - (1/3)</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</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">(2/3) / (5/12)</gadget>
<output>8/5 = around 1.6</output>

<result>8/5 = around 1.6</result>