It takes 5 hours for a car to drive from place A to place B, but it only takes 4 hours to return. Ask, by what percentage is the speed increased when returning?
汽车从甲地开往乙地需要5小时，返回时只用了4小时，问，返回时速度提高了百分之几？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/4) - (1/5)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/20) / (1/5)</gadget>
<output>1/4 = around 0.25</output>

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