Question Details

Ajay starts from Point A and drives 20 km towards South. He then takes a left turn, drives 5 km, turns left and drives 30 km. He then takes a right turn and drives 8 km. He takes a final right turn, drives 10 km and stops at Point Q. How far (shortest distance) and towards which direction should he now drive to reach Point A again? (All turns are 90° turns only.)

Options

A

13 km towards East

B

5 km towards West

C

13 km towards West

D

8 km towards West

Show Answer

Correct Answer :

Option C

13 km towards West

Solution :

To find the shortest distance and the direction Ajay needs to drive to return to Point A from Point Q, we can trace his path step-by-step using a standard two-dimensional coordinate system. Let Point A be the origin (0, 0), with the directions represented as follows:
- North corresponds to the positive y-axis direction.
- South corresponds to the negative y-axis direction.
- East corresponds to the positive x-axis direction.
- West corresponds to the negative x-axis direction.

Step 1: Start at Point A
Initial coordinates: (x_0, y_0) = (0, 0)

Step 2: Drive 20 km South
Driving South decreases the y-coordinate by 20 km.
New position: (0, 0 - 20) = (0, -20)

Step 3: Turn left and drive 5 km
Since Ajay was facing South, a left turn changes his direction to East (increasing the x-coordinate).
New position: (0 + 5, -20) = (5, -20)

Step 4: Turn left and drive 30 km
Since he was facing East, a left turn changes his direction to North (increasing the y-coordinate).
New position: (5, -20 + 30) = (5, 10)

Step 5: Turn right and drive 8 km
Since he was facing North, a right turn changes his direction to East (increasing the x-coordinate).
New position: (5 + 8, 10) = (13, 10)

Step 6: Turn right, drive 10 km and stop at Point Q
Since he was facing East, a right turn changes his direction to South (decreasing the y-coordinate).
Final position of Point Q: (13, 10 - 10) = (13, 0)

Step 7: Find the distance and direction from Point Q back to Point A
We need to travel from Point Q (13, 0) to Point A (0, 0).
The difference in coordinates is:
\Delta x = 0 - 13 = -13
\Delta y = 0 - 0 = 0

The shortest distance is the straight-line distance:
\sqrt{(-13)^2 + 0^2} = 13\text{ km}

Since the change in the x-coordinate is -13 (in the negative x direction) and there is no change in the y-coordinate, Ajay must drive directly West to reach Point A.

Therefore, Ajay needs to drive 13 km towards West to return to Point A.

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