Here, Walking to a certain place + riding back = 6 hrs 35 min. ...(i) 2 × riding the same distance = 4 hrs 35 min. ...(ii) Multiplying equation (i) × 2 and subtracting (ii) we get Time taken in walking both ways = 13 hrs 70 min – 4 hrs. 35 min = 8 hrs. 35 min.