A and B start on a circular track of length 400 m simultaneously from the same point in
opposite direction running at 5 m/sec and 3 m/sec respectively.
(i) When will they meet for the first time?
(ii) What point with respect to the starting point in the direction in which A runs will they meet?
(iii) When will they meet for the first time at the starting point?
(iv) How many times would they have met before they meet for the first time at the starting
point again?
Correct Answer: |
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C) (i) 50 seconds (ii) 250 m (iii) 400 seconds (iv) 7 times |
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Description for Correct answer:
(i) Since A and B run in opposite directions, their relative speed = 5 + 3 = 8 m/sec.
They will meet for the first time in \( \Large \frac{400}{8} \) = 50 seconds.
(ii) In 50 seconds, A would have covered a distance of \( \Large 50 \times 5 \) = 250 m from the starting point in his direction.
(iii) A will take \( \Large \frac{400}{8} \) = 80 seconds to complete one lap along the circular track.
B will take \( \Large \frac{400}{3} \) seconds to complete one lap along the circular track.
L.C.M of 80 and \( \Large \frac{400}{3} \) is 400 seconds. Therefore, A and B will meet for the first time at the starting point in 400 seconds.
(iv) As they meet each other every 50 seconds, they will meet for the first time at the starting point at the 8th time from the time they start the race and will meet once at the starting point for every 8 times they meet. i.e., they would have met 7 times before they meet at the starting point for the first time.
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