Let us consider the area model of 45.
The side lengths of 45 can be as:
5, 9 ; 1,45 ; 3,15
Let us consider the area model of 60.
The side lengths can be as:
1,60 ; 2,30 ; 4,15 ; 2,30 ; 10,6 ; 3,20
So, the common side lengths to the area models of 45 and 60 are 1, 3 , 5 and 15.
These common side lengths represents the common factors of 45 and 60 as factors are the numbers which we can multiply together to get another number and When we find the factors of two or more numbers, and then find the factors that are the same or common, then they are termed as the "common factors".
