The Green neon lights flashes every 12 seconds, the red every 7 seconds, the blue every 5 seconds. If all the lights flash together at 8:00 P.M.,

Question

then after how many minutes will they flash together again? 

 

Answer this ASAP. Thanks :)) with Solution and Answer.

Answer 1

The largest time interval is 12 seconds.  Take multiples of this number until the two smaller numbers (5 & 7) divides it without remainders.

 

 

 

12, 24, 36, 48, 60, 72, 84, 96, 108, 120, 132, 144, 156, 168, 180, 192, 204, 216, 228, 240, 252, 264, 276, 288,

 

300, 312, 324, 336, 348, 360, 372, 384, 396, 408, 420

 

 

 

Or notice the none of the numbers share prime factors, so the smallest compatible time is 5 x 7 x 12 = 420.