It takes Xiao Ming 20 minutes to go to the library from home, and it takes 16 minutes to return. How much does Xiao Ming speed up when returning?
小明从家去图书馆要20分钟，返回时用了16分钟，返回时小明的速度提高了多少．
<gadget id="calculator">1 / 16</gadget>
<output>1/16 = around 0.0625</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/16) - (1/20)</gadget>
<output>1/80 = around 0.0125</output>

<gadget id="calculator">(1/80) / (1/20)</gadget>
<output>1/4 = around 0.25</output>

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