SOLUTION: If a red light flashes every 12 seconds and a yellow light flashes every 30 seconds, what second will the flash at the same time

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Question 908783: If a red light flashes every 12 seconds and a yellow light flashes every 30 seconds, what second will the flash at the same time
Answer by jim_thompson5910(35256) About Me  (Show Source):
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They will flash together at the same time every 60 seconds, ie every minute.

Why 60? Because 60 is the LCM of 12 and 30

Multiples of 12: 12,24,36,48,60,72,84,96,108,120
Multiples of 30: 30,60,90,120,240,270,300

Notice 60 is the smallest multiple they have in common.