A job can be completed in 10 days by A and B working together. If A alone can complete it in 15 days, if B does it alone, how many more days will it take than A.
一项工作，甲、乙合作10天可以完成，若甲独做15天才能完成，若乙独做，比甲多用多少天．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/10) - (1/15)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / (1/30)</gadget>
<output>30</output>

<gadget id="calculator">30 - 15</gadget>
<output>15</output>

<result>15</result>