Answer:
78 miles
Explanation:
Given that:
Original length, L = 47 miles
Additional length (miles) added per day, = 1 mile
Representing as an equation :
L(D) = original length + additional length per day * number of days
Let, D = number of days
L(D) = 47 + D
Length after 31 days :
L(31) = 47 + 31
= 78 miles