Question

The traffic lights at three different road crossings change after every 48sec, 72sec and 108 sec respectively. If they change simultaneously at 6am, at what time will they change simultaneously again?​

Answer 1

Answer:

Given

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 a 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

Answer 2

Answer:

6:25:2 AM

Step-by-step explanation:

Step 1) LCM of 48, 72 and 108

LCM(48,72,108) = 1512

Step 2) Divide 1512 by 60(to get hours)

1512÷60 = 25.2

Step 3) Add 25.2m in 6am

= 6:25:2 AM

Hope it helps;)