Question

A recipe calls for 1.5 cups of sugar for every 1/2 teaspoons of vanilla. How much vanilla should be used for every 1 cup of sugar?

Answer 1

1.5/0.5 = 3:1 = 1 : 1/3
Not many measuring sets have 1/3 tsp spoons, however ...

Answer 2

0.5/1.5 = 1/3 teaspoons of vanilla / cup of sugar.