if it took an average man 15 mins to walk 1 mile , then he stopped for a break for 30 seconds then walked half a mile back then stopped for a further 30 seconds and returned to the end point of his original journey , how long has it took him to walk the half mile back ?
One variable unaccounted for is gradient, if the initial phase was walked downhill the return would probably take longer, if the initial phase was up hill the return would probably be quicker. Insufficient data to resolve.