Question 566914
John went every fourth day,
 Paul went every fifth day,
 George went every seventh day, and 
Stuart went every ninth day. 
How many days was it before all four went to the movies together again? 
:
What we want here is the Least common multile of 4, 5, 7, 9
The numbers do not have any common prime factors, therefore
4*5*7*9 = 1260 days before they all went to the movies together again