Make your sketch showing the man at some position.
let the distance he is from the post be x,
let the length of his shadow by y
you have similar triangles, so we have:
6/(x+y) = 2/x
2x + 2y = 6x
y = 2x
dy/dt = 2dx/dt
= 2(5) km/hr
a man of height 2 meter walk at a uniform speed of 5km/hr away from a lamp post which is 6 meter high find the rate at which length of his shadow increase
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