Question

Ian drinks 3/4 cups of water for every half-mile that he runs. In cups, how much water should Ian take along for a 31/2 mile run?

Answer 1

I assume you mean a 3 1/2-mile run.

3 1/2 miles = 7/2

7 * (3/4) = 21/4 = 5 1/4 cups

Answer 2

(3 1/2 mi)×(3/4 cups)/(1/2 mi) =
7/2 × 3/4 × 2/1 = 21/4 cups