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NDA2016MathematicsHeights and DistancesActual

A moving boat is observed from the top of a cliff of 150 m height. The angle of depression of the boat changes from 60^ to 45^ in 2 minutes. What is the speed of the boat in metres per hour?

Options

  1. A4500 3
  2. B4500( 3 -1) 3
  3. C4500 3
  4. D4500( 3 +1) 3

Correct answer

B. 4500( 3 -1) 3

Step-by-step solution

aligned & 60^ = 150 x x= 150 3 & Also, 45^ = 150 x+y & x+y=150 & y=150-x=150- 150 3 & y=150 ( 3 -1 3 )= distance travelled & Speed ( m / hr )= 150( 3 -1) 3 60 2 =4500 ( 3 -1) 3 aligned

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