The distance between Xiao Ming's home and school is 450 meters, and it usually takes 10 minutes to walk. I was in a hurry this day, and it took me 2 minutes less to go back and forth. What was his average speed for the day?
小明从家到学校距离是450米，平时要走10分钟．这天要赶时间，来回少用了2分钟．这天他的平均速度是多少？
<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">20 - 2</gadget>
<output>18</output>

<gadget id="calculator">2 / 18</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">450 * (1/9)</gadget>
<output>50</output>

<result>50</result>