You go through the times tables. i.e There isn't 36 in the 5 times table so 5 is not a factor of 36, but 36 is in the 6 times table therefore 6 is a factor of 36. (Its also in the 1 times table!)
Factors of 36 are 1, 2, 3, 4, 6, 9, 12, 18, and 36. The factors of 72 are 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, and 72. All of the factors of 36 are also factors of 72.
Since 36 is a factor of 72, the factors of 36 are included in the factors of 72.
Since 12 is a factor of 36, the factors of 12 are contained in the factors of 36.
36-24-36
36-24-36 is a good one.
36 24 36
36 24 36
36-25-36
The common factors of 27 and 36 are 1, 3 and 9.
Since 36 is a factor of 72, all of its factors are included in the factors of 72.
36 has 9 factors including 1 and 36. Its factors are: 1, 2, 3, 4, 6, 9, 12, 18, 36.
The set of factors of 72 contains the set of factors of 36.