Question

the traffic lights at three different road crossing change after every 48 seconds, 72 seconds and 108 seconds respectively. if they change simultaneously at 7 a.m., at what time will they change simultaneously again?

Answer 1

Step-by-step explanation:

first factories the respective factors.factors of 48 are:

48=2×2×2×2×3

factors of 72 are:

72=2×2×2×3×3

factors of 108 are:

108=2×2×3×3×3

so the L C M of above numbers is

L C M =2×2×2×2×3×3×3

L C M =432 seconds

now convert these seconds into minutes

so divide 432 with 60

=432 seconds= 432/60 minutes

=432/60 minutes =7 12/60

or it can also written as 7 minutes 12 seconds

so,the time that change again simultaneously is 7 minutes 12 seconds

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Answer 2

Answer:

7 minutes 12 seconds past 7 a.m.

Step by step explanation:

LCM of 48 seconds, 72 seconds and 108 seconds.

48 = 2×2×2×2×3

72 = 2×2×2×3×3

108 = 2×2×3×3×3

LCM= 2×2×2×2×3×3×3

= 432

Now,

1 minute = 60 seconds

So, divide 432 by 60...

We will get 7.2 seconds..

Now,

1 minute = 60 seconds

So, 7 minutes = 7×60 seconds= 420 seconds.

Now, Subtract 432 and 420...

= 4 3 2

- 4 2 0

0 1 2

☆Hence, 432= 7 minutes 12 seconds...

So, at 7 minutes 12 seconds past 7 a.m., they will change simultaneously again...