There are 12 inches in one foot. 120 x 12 = 1,440 inches. The correct ratio to be placed is the 5th one (aka 12 inches over 1 foot).
There are 4 terms in the expression
The mean of the data is 11
now we find the difference between the mean and each number
1, 2, 3, 0.5, 0.25, 1.25, 1.
now we square the numbers
1, 4, 9, 0.25, 0.0625, 1.
now we find the mean of the new numbers
which is 2.1875
2.1875 is your standard deviation.
20 minutes* (1 hour/ 60 minutes)* (6 miles/ 1 hour)= 2 miles.
(Note that the units cancel out so you end up getting the answer)
The final answer is 2 miles~