## Physics: Principles with Applications (7th Edition)

The number of kilometers walked per day is (12 hours)(4 km/hour) which is 48 km/day. The circumference of the Earth is $2\pi R = 2 \pi (6400)$ km $\frac{2 \pi (6400) km}{48~km/day} = 838$ days. It would take about 838 days to walk around the Earth.