Set up a ratio.
x= portion of 1 hour
4 miles/1 hour= 1 mile/ x hour
cross multiply
4 * x= 1 * 1
4x= 1
divide both sides by 4
x= 1/4 of an hour
To find number of minutes:
1 hour= 60 minutes
=1/4 of an hour * 60 minutes
=60/4
=15 minutes
ANSWER: It would take 1/4 of one hour ( or 15 minutes) to walk 1 mile.
Hope this helps! :)