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On a road three consecutive traffic lights change after 36,42 and 72 seconds respectively. If the lights are first switched on at 9:00 AM sharp, at what time will they change simultaneously?
  • a)
    9:08:04
  • b)
    9:08:24
  • c)
    9:08:44
  • d)
    None of these
Correct answer is option 'B'. Can you explain this answer?
Verified Answer
On a road three consecutive traffic lights change after 36,42 and 72 s...
Explanation:
LCM of 36, 42 and 72,
36 = 2 × 2 × 3 × 3
42 = 2 × 3 × 7
72 = 2 × 2 × 2 × 3 × 3
LCM = 2 ×2 × 2 × 3 × 3 × 7 = 504 seconds.
LCM of 36, 42 and 72 is 504
So, the lights will change simultaneously after 8 minutes and 24 seconds.
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Most Upvoted Answer
On a road three consecutive traffic lights change after 36,42 and 72 s...
Calculation of Time for Simultaneous Change of Traffic Lights:
- The time intervals at which the traffic lights change are 36, 42, and 72 seconds respectively.
- To find the time when all three lights change simultaneously, we need to find the LCM of these time intervals.
- LCM(36, 42, 72) = 504 seconds.

Conversion to Hours, Minutes, and Seconds:
- 504 seconds is equal to 8 minutes and 24 seconds (504 ÷ 60).
- Adding this time to the starting time of 9:00 AM:
- Hours: 9 + 0 = 9
- Minutes: 0 + 8 = 8
- Seconds: 0 + 24 = 24

Final Answer:
- Therefore, the traffic lights will change simultaneously at 9:08:24 AM.
- Hence, the correct answer is option 'B' (9:08:24).
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On a road three consecutive traffic lights change after 36,42 and 72 seconds respectively. If the lights are first switched on at 9:00 AM sharp, at what time will they change simultaneously?a)9:08:04b)9:08:24c)9:08:44d)None of theseCorrect answer is option 'B'. Can you explain this answer?
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