Solution:

Given height of the pole = 6 m
Length of shadow of the pole = 4 m
Let the angle be θ
tanθ = 6/4 = 3/2 → (1)
Given length of shadow of the tower = 28 m
Let the length of shadow of the tower be x
tanθ = x/28 → (2)
From (1) and (2), we get
3/2 = x/28
x = 28*3/2 = 42 m
Therefore, the length of the tower is 42 m