The greatest common factor (GCF) of 10, 15, and 20 is 5.
To find the GCF of these numbers, we first list the factors of each number:
- Factors of 10: 1, 2, 5, 10
- Factors of 15: 1, 3, 5, 15
- Factors of 20: 1, 2, 4, 5, 10, 20
The common factors of 10, 15, and 20 are 1 and 5. The greatest among these common factors is 5. Therefore, the GCF of 10, 15, and 20 is 5.