Answers

2016-02-17T19:53:53+05:30
Let AB be boy = 1.5m
CD be lamp = Let it be x m.
OB be shadow cast by boy = 4.5m
BD be distance between boy and lamp = 3m

Therefore
In ΔAOB,
=> tan θ = AB/OB
In 
ΔCOD,
=> tan θ = CD/OD = CD/(OB+BD)

∴ AB/OB = CD/(OB+BD)
=> 1.5/4.5 = CD/(4.5+3)
=> CD = 7.5/3 = 2.5m
2 2 2
See diagram for details on this problem.