Percent of Decrease!!!?

Question

Help me with this problem:

A can of juice used to contain 6 ounces. Now it contains 5.5 ounces

a. What is the percent of decrease

b. If the cans were sold in a 6-pack for $1.59 what was the percent of increase per ounce?

Answer 1

a 6 - 5.5 / 6
b Doesn't make sense. "Percent" is per hundred, you can't have "per hundred per ounce".