An aeroplane flying horizontally at a height of 3 Km. above the ground is observed at a certain point on earth to subtend an angle of 60°. After 15 sec flight, its angle of elevation is changed to 30°. The speed of the aeroplane (taking √3 = 1.732) is
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Correct answer: B
Explanation
The correct answer is option 2
tan 60 = 3/BC
BC = 3/√3 = √3
tan 30 = 3/AC
AC = 3√3
AB = AC - BC = 3√3 - √3 = 2√3
Speed of airplane = 23×1000/15 = 230.93 m/s