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Math

A lighthouse flashes its light every 12 minutes. Another lighthouse every 18 minutes. If the two lighthouses flash together at 12:00 noon,at what time will they next flash together?

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  1. Easy way: from a start at 0,
    first lighthouse flashes at 12,24,36,48,60,72,84,... minutes
    2nd lighthouse flashes at 18,36,....
    so my "guess" would be at 12:36
    (that was too easy)

    rigorous math approach
    12 = 2*2*3
    18 = 2*3*3
    LCM = 2*2*3*3 = 36
    so time is 12:36

    btw, a lighthouse that flashes only every 18 minutes would
    be useless and downright dangerous to depend on.
    Are you sure it wasn't seconds? The solution would then be
    12:00:36

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  2. Bobo ampota

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