Colin ran his first mile in 6 minutes.  He ran his next two miles in 5 minutes each and finished his 4th mile in 4 minutes.  What was the average time it took him to run a mile?
His first mile was in 6 minutes, then 5 minutes, another 5 minutes and his final mile was 4 minutes so it took him 6+5+5+4 = <<6+5+5+4=20>>20 minutes
It took 20 minutes to run 4 miles so his average time was 20/4 = <<20/4=5>>5 minutes per mile
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