A man on the top of a vertical tower observes a car moving at a uniform speed towards the tower on a horizontal road. If it takes 18 min for the angle of depression of the car to change from 30 ° to 45 ° , then the time taken (in min ) by the car to reach the foot of the tower is

Question

A man on the top of a vertical tower observes a car moving at a uniform speed towards the tower on a horizontal road. If it takes 18 min for the angle of depression of the car to change from 30 ° to 45 ° , then the time taken (in min ) by the car to reach the foot of the tower is, 9 2 3 - 1, 18 1 + 3, 18 3 - 1, 9 1 + 3

MARKS App · Accepted Answer

Let length of tower be h . ⇒ A C ′ = A B = h And A C = A B cot 30 ° = 3 h ⇒ C C ′ = 3 - 1 h Time taken by car form C C ' = 18 min ⇒ Time take by car to reach the foot of the tower = 18 3 - 1 min = 9 3 + 1 min

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