a man is walking away from a light pole at a rate of 5 feet

Solution

s is shadow length, d is distance of man from pole, t is time s/(s+d)=6/20 s=.3*(s+d) .7*s=.3*d s=.3/.7*d ds/dd=3/7 dd/dt=5 So ds/dt=5*3/7=2.143