Question

8. The traffic lights at three different road
crossings change after every 36 seconds, 48
seconds and 84 seconds respectively. If they
change simultaneously at 8 a.m., at what
time will they change simultaneously again?​

Answer 1

Step-by-step explanation:

Given that traffic light at three different road crossing change after every 48 seconds,72 seconds and 108 seconds respectively. Hence,after 7 min and 12 seconds they will blink simultaneously. ... If at some point they were changing simultaneously, they will continue to do so every 432 seconds.

Answer 2

Answer:

Step-by-step explanation:

The traffic light at three different road crossing change after every 48 seconds,72 seconds and 108 seconds respectively.

So let us take the LCM of the given time that is 48 seconds, 72 seconds, 108 seconds

⇒ 48 = 2 × 2 × 2 × 2 × 3

⇒ 72 = 2 × 2 × 2 × 3 × 3

⇒ 108 = 2 × 2 × 3 × 3 × 3

Hence LCM of 48, 72 and 108 = (2 × 2 × 2 × 2 × 3 × 3 × 3)

LCM of 48, 72 and 108 = 432

So  after 432 seconds they will change simultaneously

We know that

60 seconds = 1 minute

so on dividing 432 / 60 we get 7 as quotient and 12 as reminder

Hence, 432 seconds = 7 min 12 seconds

∴ The time  = 7 a.m. + 7 minutes 12 seconds

Hence the lights change simultaneously at  7:07:12 a.m