The only common factor of 4 and 5 is 1. 4 and 5 are common factors of 20 and 40.
1,2,4
4
The greatest common factor (GCF) is 2.
20, among others.
20 and 40.
12
The factors of 10 are 1, 2, 5, and 10. The factors of 5 are 1 and 5. The common factors of 10 and 5 are 1 and 5.
The GCF is: 1
20
The common factors are 1 and 5.
240
Any multiple of 12.