Multiple choice

During the shooting of a super hit film 'MARD' Amitabh Bachchan was waiting for his beloved 'Amrita Singh' with his dog. When he saw her approaching, the dog was excited and dashed to her then back to master and so on, never stopping. How far would you estimate the dog ran if its speed is $30$ km/hr and each of them walked at $4$ km/hr, starting from a distance $400$m apart?

  1. $400$ m
  2. $880$ m
  3. $1500$ m
  4. $30$ km
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The dog runs at a constant speed of 30 km/hr for the entire duration that the two people are walking toward each other. The time taken for them to meet is distance / relative speed = 0.4 km / (4 + 4) km/hr = 0.05 hours. The distance the dog runs is speed * time = 30 km/hr * 0.05 hr = 1.5 km, which is 1500 m.

AI explanation

The two people start 400 meters apart and walk towards each other at 4 km/hr each, giving a relative closing speed of 8 km/hr, which converts to 8000 meters per hour. The total time taken for them to meet is the initial distance divided by their relative speed, giving 400/8000 hours or 1/20 of an hour. The dog runs continuously at 30 km/hr during this time, so the total distance it covers is 30 multiplied by 1/20, equaling 1.5 kilometers, which is 1500 meters.

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