Question

the traffic lights at three different road crossings change after every 48 seconds, 72 seconds and 100 seconds. if they start changing simultaneously at 8:00 a.m.,after how much time will they change again Simultaneously please solve fast​

Answer 1

Answer:

at 9 A.M

Explanation:

the LCM of 48, 72 amd 100 is 3600.

So the lights will again change together after 3600 sec.

if we convers 3600 sec into mintuve i.e (3600/60)=60 minute i.e nothing but 1 hr.

so, 8 a.m+1 hr= 9am.(the ans)

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