20 minutes is 20/60=1/3 of an hour.
Ms. Warren ran 6/3=<<6/3=2>>2 miles.
30 minutes is 30/60=1/2 of an hour.
Ms. Warren walked 2/2=<<2/2=1>>1 mile.
Ms Warren ran and walked 2+1=<<2+1=3>>3 miles in total.
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