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January 29, 2015

January 29, 2015

Posted by **chelsea** on Sunday, September 26, 2010 at 4:38am.

- maths -
**Reiny**, Sunday, September 26, 2010 at 7:04amfirst lighthouse will flash in 56 sec, then 112, 168 , etc seconds

second lighthouse will flash in 49 sec, then 80, 120, etc seconds

so this is just like finding the LCD of 56 and 40

56 = 2x2x2x7

40 = 2x2x2x5

LCD = 2x2x2x5x7 = 280

so they will flash together 280 seconds from now or 4 minutes and 40 seconds from 9 pm

which would be 9:04:40 pm

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