Question

An electric post casts a shadow of lengh 20m at a time when a tree 6m high casts a shadow of length 8m. Find the height of than pole

Answer 1

since the sun subtends an equal angle on both the objects 
so tanx will be a constant.

tanx=6/8        (from tree's data)

tanx=H/20   (post data)
6/8=H/20

H=120/8
  =15