It takes 5 hours for a passenger ship to sail against the current from point A to point B. When returning, it takes 1 hour less to sail along the current than to sail against the current. How much is the speed increased when returning?
一艘客轮从甲地逆水航行至乙地需要5小时，返回时顺水航行比逆水航行少用1小时，返回时速度提高了百分之几？
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<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>