Greatest Common Factor:
The greatest common factor, or GCF, is the greatest factor that divides two numbers.
Given Numbers : 42 & 30
Factors of 42 : 7x3x2x1, 7x6x1,
Factors of 30=5x3x2x1, 5x6,1
Here the common factors of 42 & 30 are : 6,3, 2, 1
The greatest number in 6, 3, 2, 1 is 6
So, the greatest common factor is 6
The greatest common factor of 42 & 30 is 6
Answer: B) 6