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Question

Arvind starts from Point A and drives 25 km towards east. He then takes a right turn, drives 10 km, turns left and drives 20 km. He then takes a left turn and drives 10 km. He takes a final left turn, drives 12 km and stops at Point P. How far (shortest distance) and towards which direction should he drive in order to reach Point A again? (All turns are 90-degree turns only, unless specified.)

The correct answer is
33 km towards west

To determine the shortest distance and direction from Point P back to Point A, we need to track Arvind's movements using a coordinate system.

Mapping Arvind's Driving Path

Let's assume Point A is the origin (0, 0) on a 2D plane, with East along the positive x-axis and North along the positive y-axis.

  • Start at A: (0, 0)
  • Move 1: 25 km East. New position: (0 + 25, 0) = (25, 0).
  • Move 2: Takes a right turn (now facing South), drives 10 km. New position: (25, 0 - 10) = (25, -10).
  • Move 3: Turns left (now facing East), drives 20 km. New position: (25 + 20, -10) = (45, -10).
  • Move 4: Turns left (now facing North), drives 10 km. New position: (45, -10 + 10) = (45, 0).
  • Move 5: Takes a final left turn (now facing West), drives 12 km. New position: (45 - 12, 0) = (33, 0). This is Point P.

Calculating Return Journey from P to A

Arvind's final position is Point P at coordinates (33, 0). Point A is at the origin (0, 0).

To return from Point P (33, 0) to Point A (0, 0), Arvind needs to cover the displacement from P to A.

  • Change in East-West direction (x-axis): $0 - 33 = -33$ km. A negative value indicates movement towards the West.
  • Change in North-South direction (y-axis): $0 - 0 = 0$ km.

The required movement is 33 km towards the West.

Determining Shortest Distance and Direction

The shortest distance is the magnitude of the displacement vector ($-33, 0$).

Distance = $\sqrt{(-33)^2 + (0)^2} = \sqrt{1089} = 33$ km.

The direction is determined by the displacement vector components. Since the x-component is -33 (West) and the y-component is 0, the direction is West.

Therefore, Arvind needs to drive 33 km towards West to reach Point A again.

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Important Questions from Direction and Distance (Notes)

  1. If a map is placed in such a manner that east becomes southeast, then what will northeast become?
  2. Point A is $30$ m to the North of point B. Point A is $10$ m to the west of point C. Point C is $20$m to the North of point D. Point E is $20$ m to the East of point D. Point F is $20$ m to the South of point E. What is the shortest distance from the point B to point E.

  3. Rakesh left home and walked $5$km southwards, then turned right and walked $2$km and again turned right and walked $5$ km and finally again turned left and walked $5$ km. The shortest distance between the final position and home is.

  4. The door of Aman's house faces east. From the back side of his house, Aman walks straight 30m. Again he walks 20m after turning to his left, then he turns to his right and walks 30m. Finally he turn towards north and walks 20m and stops. So, what is the distance between the starting and the end point?
  5. Smitha runs 10 km south from her flat, turns left and walks 23 km again turns left and walks 40 km then turns right and walks 5 km to reach her office. In which direction is the office from her house?
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