Given, the drunkard walks 7 steps forward and 4 steps backward.
So, the net displacement undertaken by the drunkard = 3 steps in one stroke
Also given, length of 1 step = 0.5 m
Time taken to take 1 step = 1 sec
∴ Displacement in 1 stroke = 3 x 0.5=1.5m
Displacement in 3 strokes = 3 x 1.5 =4.5m
Time taken to walk one step is 1 sec.
Since to complete one stroke, drunkard walks 7 steps forward and 4 steps backward i.e. total of 11 steps, therefore drunkard takes 11s to complete one stroke.
Time taken to complete three strokes, t = 11 x 3 = 33s
Now, average velocity of drunkard is given by,