SOLUTION: Can some one show me how to solve this problem? Earth, Jupiter, Saturn, and Uranus all revolve around the sun. Earth takes 1 year, Jupiter 12 years, Saturn 30 years, and Uranus 84

Question 82360: Can some one show me how to solve this problem?
Earth, Jupiter, Saturn, and Uranus all revolve around the sun. Earth takes 1 year, Jupiter 12 years, Saturn 30 years, and Uranus 84 years. How frequently do these four Planets line up with each other?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Earth, Jupiter, Saturn, and Uranus all revolve around the sun. Earth takes 1 year, Jupiter 12 years, Saturn 30 years, and Uranus 84 years. How frequently do these four Planets line up with each other?
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You need to find the least common multiple of 1,12,30,84
Express each number as a product of primes:
1 = 1
12= 2^2*3
30=2*3*5
84=2^2*3*7
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lcm = 2^2*3*5*7=420
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They will line up once in every 420 years.
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Cheers,
Stan H.
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