So LCM stands for "least common multiple" While GCF is "greatest common factor"
Let's look at your number 1 (3&6)
3,6,9,12 6,12,18,24
Both times table has 6 in them making 6 the LCM
To find the GCF we need to know what can go into 3 equally. Since 3 is prime the greatest factor for 3 is....3. 6 goes into 3 two times so 3 is the GCF.
LCM:6 GCF:3
Lets do number 10 (40&4)
For LCM you see whats the smallest number that is in both times tables
4,8,12,16,20,24,28.......40 40,80, 160....
40 is the LCM because 40 is what's the smallest number between the two
GCF?
4 times 1 equals 4. Nothing bigger than 4 can make 4 (if your multiplying). That makes 4 automatically the GCF. :)
