Obviously, I leave home for school at 7:00 every morning and arrive at school at 7:30. One day, when he left home at 6:50, he thought: "I leave early today, so I can walk slowly." So he walked 10 meters less than usual every minute, and as a result, he arrived at school 5 minutes later than usual. How many meters away is Mingming's home from the school?
明明每天早上7：00从家出发上学，7：30到校．有一天，明明6：50就从家出发，他想："我今天出门早，可以走慢点．"于是他每分钟比平常少走10米，结果他到校时比往常迟到了5分钟．明明家离学校多少米．
<gadget id="calculator">10 * 30</gadget>
<output>300</output>

<gadget id="calculator">10 * 15</gadget>
<output>150</output>

<gadget id="calculator">300 + 150</gadget>
<output>450</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/30) * 30</gadget>
<output>1</output>

<gadget id="calculator">(1/30) * 15</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">1 + (-1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">450 / (1/2)</gadget>
<output>900</output>

<result>900</result>