What is the lenght in miles of the field

(Perimeter/6)2= Length

Ok this is what you do it went 12 miles and hour to travel the perimeter in 7.5 minuets there are 60 min in an hour do 12/60 thats 0.2 miles every min do 7.5x0.2=1.5 so the perimeter is 1.5 miles but you are looking for length so the length would be 0.5 because that mean the width would have to be 0.25 and 

The length is 0.5miles 

(6,0) i hope it makes enough sense