A piece of work can be completed in (1/3) hours alone, and B can be completed in (1/4) hours alone, how many hours can A and B work together to complete.
一件工作，甲独做要(1/3)小时完成，乙独做要(1/4)小时完成，如甲、乙合做多少小时可以完成．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / (1/3)</gadget>
<output>3</output>

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

<gadget id="calculator">1 / (1/4)</gadget>
<output>4</output>

<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<result>1/7 = around 0.142857</result>