A project is completed in 15 minutes by A alone, and (1/3) hour by B alone, how much slower is B's work efficiency than A.
一项工程，甲独做15分钟完成，乙独做(1/3)小时完成，乙的工作效率比甲慢多少．
<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">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

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

<gadget id="calculator">4 - 3</gadget>
<output>1</output>

<result>1/4 = around 0.25</result>