A 1.2 m tall girl spots a balloon movingwith the wind in a horizontal line at aheight of 88.2 m from the ground. Theangle of elevation of the balloon fromthe eyes of the girl at any instant is60°. After some time, the angle ofelevation reduces to 30° (see Fig. 9.13).Find the distance travelled by theballoon during the interval.


From this figure:

BF = 1.2 m,


AG = 88.2 m,


AC = AG – GC


= 88.2 – 1.2


= 87 m


EBD = 30° and ABC = 60°,


CD = ?


In Δ ABC;






In Δ ABC,






Now, the distance covered by the balloon will be:


CD = BD – BC


CD =


CD = 5


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