Question 1050941
 Kasey and Joe were walking on a circular track.
 It took Kasey 21 min. to go one mile, and Joe 18 min.
 How many minutes before they see each other again? 
:
Find the Least common multiple of 21 and 18, using prime factoring
21: 3 * 7
18: 2 * 3 * 3
LCM: 2 * 3 * 3 * 7 = 126 min