Question

What is the GCF of 90 and 190?

Answer 1

   90              190     
1 × 90        1 × 190
2 × 45        2 × 95
3 × 30        5 × 38
5 × 18      10 × 19
6 × 15
9 × 10
 GCF: 10

Answer 2

Let's first find out their factors.

90's factors are : 

$1,2,3,5,6,9,10,15,18,30,45,90$

190's factors are :

$1,2,5,10,19,38,95,190$

The common factors of 90 and 190 are :

1,2,5 and 10. 

The greatest one among these is, 10. So the greatest factor of 90 and 190 is 10.