Brinlyn increased the amount of water she drank per day from 32 oz to 40 oz. By what percentage did Brinlyn increase the amount of water she drank each day?
To find the percentage increase in the amount of water Brinlyn drank per day, we need to divide the increase in ounces by the original amount and then multiply by 100%.
The increase in the amount of water she drank per day is 40 oz - 32 oz = 8 oz.
The original amount Brinlyn drank per day is 32 oz.
The percentage increase is (8 oz / 32 oz) * 100% = 25%. Answer: \boxed{25}.