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posted by dan on Sunday, July 29, 2012 at 5:22pm.

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?

hint: what is the LCM of 3,7, and 18 ?

72

72/7 = ? Try again.

Oops I was thinking of 8 times 9 It's 126

Right.

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