Q. 144.4( 238 Votes )

# A 1.2 m tall girl spots a balloon moving with the wind in a horizontal line at a height of 88.2 m from the ground. The angle of elevation of the balloon from the eyes of the girl at any instant is 60°. After some time, the angle of elevation reduces to 30° (see Fig. 9.13).Find the distance traveled by the balloon during the interval.

Answer :

From this figure:

BF = height of girl = 1.2 m,

AG = height of balloon from ground initially = 88.2 m,

AC = AG – GC

= 88.2 – 1.2

= 87 m

∠EBD = 30° and ∠ABC = 60°,

CD = ?

In Δ ABC;

where p = perpendicular and b is base

In Δ ABC,

Now, the distance covered by the balloon will be:

CD = BD – BC

CD = 58√3 m

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