Q21 of 25 Page 9

A 1.5 m tall boy is standing at some distance from a 30 m tall building. The angle of elevation from his eyes to the top of the building increases from 30° to 60° as he walks towards the building. Find the distance he walked towards the building.

To find: Distance travelled


Formula Used:



Explanation:



Let the initial point of boy is Z and final point is x


Z x is the distance he walked.


OP = OY-PY


OP = 30-1.5 ⇒ 28.5 m.


In ∆OPA,




⇒ AP = 28.5√3 …. (1)


In ∆OPB,






AB = AP-BP






= 19 √3 m


Therefore, the walking distance of boy is 19√3 m.


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