It took Zhang Qiang 2 hours to go from A to B by bicycle, and only 1.6 hours to return. How much did Zhang Qiang speed up when he returned?
张强骑自行车从甲地到乙地用了2小时，返回时只用了1.6小时，张强返回时速度提高了百分之几？
<gadget id="calculator">1 / 1.6</gadget>
<output>0.625</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">0.625 - (1/2)</gadget>
<output>0.125</output>

<gadget id="calculator">0.125 / (1/2)</gadget>
<output>0.25</output>

<result>0.25</result>