In a scientific procedure, the scientist asked a question or several questions based on an observation. After asking such questions, the scientist must form a hypothesis based on the observations made and design an experiment. Hypothesis is an educated guess necessary in a scientific procedure.
Answer: 4 ft/s
Explanation:
Given
height of man
speed of person 
height if street light
Let x be the distance between person and street light and y be the length of his shadow
From diagram
as the two triangle ADE and ABC are similar therefore we can say that




differentiate above Equation w.r.t time we get

