Question

The traffic lights at three different road crossings change after every 48 seconds 72 seconds and 108 seconds If they start changing simultaneously at 8am after how much time will they change again simultaneously​

Answer 1

Step-by-step explanation:

the the traffic lights at three different road crossings change after every 48 seconds after that 72 seconds and 108 seconds if they start in his ability at 8:00 a.m. after how much time will the change again similarly

Answer 2

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If the traffic lights change simultaneously at 8 a.m, then they will change simultaneously again after the LCM of the duration i.e. 48 s, 72 s and 108 s.

LCM of these durations by prime factorisation

• 48 = 2 × 2 × 2 × 2 × 3 = 2⁴ × 3
• 72 = 2 × 2 × 2 × 3 × 3 = 2³ × 3²
• 108 = 2 × 2 × 3 × 3 × 3 = 2² × 3³

LCM of 48, 72 and 108 is 2⁴ × 3³ = 432 seconds.

Hence, They will change after 432 seconds i.e. 7 minutes 12 seconds.

The traffic lights will change after:

8 am + 7 minutes 12 seconds

08 : 07 : 12 am