A drunkard is walking along a straight road. He takes five steps forward and three steps backward and so on. Each step is 1 m long and takes 1 s. There is a pit on the road 11 m away from the starting point. The drunkard will fall into the pit after 

Since the last five steps covering 5 m land the drunkard fell into the pit, the displacement prior to this is (11 - 5) m=6 m. Time taken for first eight steps (displacement in first eight steps = 5 - 3 = 2 m) = 8 s. Then time taken to cover first 6 m of journey $=\frac{6}{2}\times 8=24s$

Time taken to cover last 5 m = 5 s
Total time = 24 + 5 = 29 s