C = 2πr
where C is the circumference and r is the radius.
Substituting the given to the equation,
C = 2π(6.38 x 10³)
C = 12760π km
We determine the number of hours that needs to be spent in order to walk around the calculated circumference. This can be calculated through the equation.
t = distance / speed
Substituting the known values,
t = (12760π km) / (4 km/h)
t = 3190π hours
Then, we calculate for the number of days given that only 12 hours is spent per day for the walk.
number of days = (3190π hours) / (12 hours/day)
number of days = 835.14 days
ANSWER: 635.14 days