UPSC Prelims 2005·GS1·science-and-technology·science and technology

Aryan runs at a speed on 40 metre/minute. Rahul follows him after an interval of 5 minutes and runs at a speed of 50 metre/minute. Rahul’s dog runs at a speed of 60 metre/minute and starts along with Rahul. The dog reaches Aryan and then comes back to Rahul, and continues to do so till Rahul reaches Aryan. What is the total distance covered by the dog?

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Last updated 23 May 2026, 3:31 pm IST
  1. A600 metres
  2. B750 metres
  3. C980 metres
  4. D1200 metresCorrect

Explanation

To find the total distance covered by the dog, we first need to determine how long the dog was running. The dog runs for the exact same amount of time it takes Rahul to catch up to Aryan. First, calculate the head start Aryan has. Aryan runs at 40 metres per minute for 5 minutes, covering 200 metres. Next, find the time Rahul takes to catch Aryan using their relative speed. The relative speed is 50 minus 40, which equals 10 metres per minute. To cover the 200 metre gap at 10 metres per minute, Rahul takes 20 minutes. Since the dog runs continuously at a constant speed of 60 metres per minute for these 20 minutes, the total distance covered by the dog is 60 multiplied by 20, which equals 1200 metres. Therefore, option D is the correct answer.
science-and-technology: Aryan runs at a speed on 40 metre/minute. Rahul follows him after an interval of 5 minutes and runs at a speed of 50 met
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