Two neon lights are turned on at the same time. One blinks every 4 seconds and the other blinks every 6 seconds. In 60 seconds, how many times will they blink at the same time?

Question

Two neon lights are turned on at the same time. One blinks every 4 seconds and the other 	blinks every 6 seconds. In 60 seconds, how many times will they blink at the same time?

owlfred · Answer

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dumbcow · Answer

Find common multiples of 4 and 6:
4  8  12  16  20  24  28  32  36  40  44  48  52  56  60
6  12  18  24  30  36  42  48  54  60
At 12,24,36,48,60 they match
Another way of looking at it is find LCM of 4 and 6, which is 12
then just count by 12's
60/12 = 5
In 60 sec, they blink at same time 5 times

anonymous · Answer

Great way to explain made it so easy.