Question

On the coast there are three lighthouses.

•The first light shines for 3 seconds, then is off for 3 seconds.

•The second light shines for 4 seconds, then is off for 4 seconds.

•The third light shines for 5 seconds, then is off for 5 seconds.

All three lights have just come on together.

1) When is the first time all three lights will be off at the same time?

2) When is the next time all three lights will come on together at the
same moment?

Answer 1

Answer:

1- after 5 Seconds

2- after 120 Seconds

Step-by-step explanation:

Answer 2

Answer:

1) 60 sec

2) 120 sec

GIVEN- all three lights

FIND- time of light will be off

Step-by-step explanation:

1) first time all three lights will be of the same time

LCM of all three lights = 3 , 4 , 5

3×4×5= 60 so after 60 second all lights off same time.

2) when next time all light come together will is

next time= 60×2= 120

so, after 120 sec then will come together.

FINAL ANSWER- 1) 60 sec 2) 120 sec

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