What is the greatest common factor of 210 and 90
The prime factorization of 210 is 2 × 3 × 5 × 7.
The prime factorization of 90 is 2 × 3 × 3 × 5.
The factors common to both numbers are 2, 3, and 5.
Multiply these factors together: 2 × 3 × 5 = 30.
Therefore, the greatest common factor of 210 and 90 is 30.