Determine which ratio forms a proportion with 10/6 by using cross products.
30/9
20/9
15/12
30/18
Cross products of 10/6 and 30/9:
(10 x 9) = (6 x 30)
90 = 180
This is not true, so 30/9 does not form a proportion with 10/6.
Cross products of 10/6 and 20/9:
(10 x 9) = (6 x 20)
90 = 120
This is also not true, so 20/9 does not form a proportion with 10/6.
Cross products of 10/6 and 15/12:
(10 x 12) = (6 x 15)
120 = 90
This is not true, so 15/12 does not form a proportion with 10/6.
Cross products of 10/6 and 30/18:
(10 x 18) = (6 x 30)
180 = 180
This is true, so 30/18 forms a proportion with 10/6.
Therefore, the correct ratio is 30/18.