Lihaan walks 8 m towards South from his office to reach a park. He then turns…

2024

Lihaan walks 8 m towards South from his office to reach a park. He then turns left and walks 15 m to reach a traffic signal. From there, he turns 90° anticlockwise and walks 8 m to reach a coffee shop. From the coffee shop, he turns left and walks 8 m to reach home. What is the horizontal distance between Lihaan's office and the coffee shop, and in which direction is the coffee shop from Lihaan's office?

  1. A.

    15m, East

  2. B.

    15 m, West

  3. C.

    12m, East

  4. D.

    12m, West

Show answer & explanation

Correct answer: A

Concept: In a direction-sense problem, track the walker's net displacement along two perpendicular axes (North-South and East-West). A left turn rotates the current facing direction 90° anticlockwise and a right turn rotates it 90° clockwise; a stated "90° anticlockwise" turn behaves exactly like a left turn. Two straight-line legs walked in exactly opposite directions cancel each other out, so only the leg(s) along the axis that does not cancel decide the final direction and distance.

Application -- tracing each leg from the office:

  1. Office to park: facing South, walks 8 m South.

  2. Park to traffic signal: at the park he turns left. A left turn while facing South changes the facing to East, so he walks 15 m East to the traffic signal.

  3. Traffic signal to coffee shop: he turns 90° anticlockwise -- the same rotation as a left turn -- so the facing changes from East to North, and he walks 8 m North to the coffee shop.

  4. Netting the two vertical (South-North) legs: the 8 m walked South (office to park) and the 8 m walked North (traffic signal to coffee shop) are equal and opposite, so they cancel completely -- the coffee shop lies on the same horizontal line as the office.

  5. With the vertical component cancelled, the only surviving displacement is the 15 m Eastward leg from the park to the traffic signal, so the coffee shop is 15 m East of the office.

Cross-check: the diagram below places the office and the coffee shop on the same top edge of a rectangle, 15 m apart, with the park and the traffic signal directly below them on the bottom edge -- confirming the office and coffee shop differ only in the East-West direction, by exactly 15 m. (The final leg to home, from the coffee shop, describes a point beyond this question and does not affect the office-to-coffee-shop distance being asked.)

Therefore, the coffee shop is 15 m East of Lihaan's office.

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