The factors of 200 are 1, 2, 4, 5, 8, 10, 20, 25, 40, 50, 100, and 200 .
The factors of 140 are 1, 2, 4, 5, 7, 10, 14, 20, 28, 35, 70, and 140 .
The factors common to both are 1, 2, 4, 5, 10, and 20 .
The greatest one of those is <em><u>20</u></em> .