Xiao Ming's home is 4,500 meters away from the school. He starts at 7:20 every morning, rides at an average speed of 250 meters per minute, and arrives at school just on time. One minute after he set off one day, he found that he didn't bring the book with him, so he went home to get it immediately. From the beginning back to the school, how fast should he ride the bicycle so as not to be late? (It takes 1 minute to pick up the book)
小明家距离学校4500米，他每天早上7：20出发，以平均每分钟250米的速度骑车，刚好准时到校．一天他出发1分钟后，发现书没带，立即回家拿，从开始返回到到达学校，以多快的速度骑车才能不迟到？(拿书用1分钟)
<gadget id="calculator">4_500 + 250</gadget>
<output>4_750</output>

<gadget id="calculator">4_500 / 250</gadget>
<output>18</output>

<gadget id="calculator">18 - 1 - 1</gadget>
<output>16</output>

<gadget id="calculator">4_750 / 16</gadget>
<output>2_375/8 = around 296.875</output>

<result>2_375/8 = around 296.875</result>