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A red light flashes 3 times per minute,green light flashes 4 times per minute and yellow light flashes 6 times per minute at regular intervals.If all

lights start flashing at the same time,how many times do they flash together in each 75 minute?


Red light flash in interval  of 20 second
green ----------//-------------of 15 second
yellow ------------//---------- of 10 second
interval 75*60 second
lcm of (20,15,10) =60
that means every 60 second they flash together once!
they flash together 75 times
5 4 5
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