Use cross products to see if each pair of ratios forms a proportion.
To see if two ratios form a proportion, we can use the cross product rule which states that for two proportions, the product of the means is equal to the product of the extremes.
For example, let's consider the ratios 1:2 and 4:8:
Cross product of first ratio = 1 * 8 = 8
Cross product of second ratio = 4 * 2 = 8
Since the cross products are equal, the two ratios 1:2 and 4:8 form a proportion.