Question 204092: Planets A, B, and C orbit a certain star once every 3, 7, and 18 months, respectively. If the three planets are now in the same straight line, what is the smallest number of months that must pass before they line up again?
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! Planets A, B, and C orbit a certain star once every 3, 7, and 18 months, respectively. If the three planets are now in the same straight line, what is the smallest number of months that must pass before they line up again?
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That is the LCM, or least common multiple, of the 3 numbers.
Since 3 is a factor of 18, it can be ignored, and the LCM is 7*18
= 126 months.
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BTW, celestial objects "in a straight line" is called a syzygy.
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