Let's first find out their factors.
90's factors are :
[tex]1,2,3,5,6,9,10,15,18,30,45,90[/tex]
190's factors are :
[tex]1,2,5,10,19,38,95,190[/tex]
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.