It took Xiao Ming 15 minutes to go from home to the library, and only 12 minutes to return. The return speed is the speed when he went.
小明从家到图书馆，去时用了15分钟，回来时只用了12分钟，返回的速度是去时速度的多少．
<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">1 / 12 / (1/15)</gadget>
<output>5/4 = around 1.25</output>

<result>5/4 = around 1.25</result>