The factor of 18 is______ From which four numbers are selected to form a proportion______ .

The factor of 18 is______ From which four numbers are selected to form a proportion______ .

The factors of 18 are: 1, 2, 3, 6, 9, 18; 1:2 = 3:6; or 3:9 = 6:18; (the answer is not unique). So the answer is: 1, 2, 3, 6, 9, 18; 1:2 = 3:6