Lesson 5 of 15
When two step counts meet
Show on a big screenA market bus leaves every 12 minutes. A station bus leaves every 18 minutes. Both leave together at 0.
Loading lab…
Step 1 of 4
- Steps of 12: 12, 24, 36.
- Steps of 18: 18, 36.
- Both reach 36.
- LCM(12, 18) = 36.
Two lists, and where they touch
The buses leave together again at minute 36.
Counting in 12s gives the multiples of 12: 12, 24, 36. Counting in 18s gives 18, 36.
A number on both lists of multiples is a common multiple. The lists first have 36 in common. That is the lowest common multiple, or LCM.
LCM(12, 18) = 36 means: the LCM of 12 and 18 is 36.
Multiples of 4 are 4, 8, 12. Multiples of 6 are 6, 12. They first share 12. So LCM(4, 6) = 12.
Try the lab to finish this lesson.