Three runners A, B, and C start together from the same point around a circular track. Their lap times are A: 252 s, B: 308 s, and C: 198 s. After how much time will they next be together at the starting point?

Difficulty: Medium

Correct Answer: 46 min and 12 s

Explanation:


Introduction:
When several runners start together and repeat laps with different lap times, their next common meeting at the start occurs after a time equal to the least common multiple of their lap times.


Given Data / Assumptions:

  • A lap: 252 s
  • B lap: 308 s
  • C lap: 198 s
  • All start together at the same point


Concept / Approach:
Compute LCM(252, 308, 198). Convert the resulting seconds to minutes and seconds for a readable time format.


Step-by-Step Solution:

LCM(252, 308, 198) = 2772 s 2772 s = 46 min and 12 s


Verification / Alternative check:
Prime factorizations confirm that 2772 is divisible by 252, 308, and 198, and there is no smaller positive time that satisfies all three simultaneously.


Why Other Options Are Wrong:
26 min 18 s, 42 min 36 s, 45 min, and 44 min are not common multiples of all three lap times.


Common Pitfalls:
Taking a simple sum or pairwise LCM instead of the LCM of all three values. Always combine all periods.


Final Answer:
46 min and 12 s

More Questions from Problems on H.C.F and L.C.M

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