A car travels from city A to city B, traveling for 5 hours and returning for 4 hours. How much speed has been increased when returning
一辆汽车从A城开往B城，去时行了5小时，返回时行了4小时．返回时的速度提高了多少
<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>