The train from Dalian to Shenyang used to arrive at 5 o'clock, but now it only takes 4 o'clock. How much has the speed of the train increased.
大连到沈阳火车原来要5时到达，现在只要4时．火车的速度提高了多少．
<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>