What are the methods to judge whether the four numbers are proportional

What are the methods to judge whether the four numbers are proportional

The basis of judging whether four numbers can form a proportion is the basic property of proportion. The method is: whether the product of the largest number × the smallest number is equal to the product of the other two numbers. If they are equal, four numbers can form a proportion; if they are not equal, they cannot form a proportion. For example, judge whether the following two groups of numbers 2, 3, 4, 6; and 3, 5, 6, 7 can form a proportion

Which group of four numbers can make up the proportion? Write out the proportion
2. 3, 4, 5, 1 / 3, 4 / 3, 4, 9

1 / 3, 4 / 3, 4 / 3, 9 / 3
1/3:3/4=4:9
1/3:4=3/4:9

4: The ratio of 6 and 8:12 is (), and the ratio can be written as () or ()

4: 6 and 8:12, their ratio is (2 / 3), the composition ratio can be written as (8:12 = 4:6) or (4:6 = 8:12)