You need to purchase juice for a party. the juice is sold for $3 per gallon or $2.50 per quart. you will need 12 oz for each of the 30 students in the class. how much juice will you need

To determine the amount of juice you will need you will multiply the number of students by how much juice each student will get.  This is the idea of grouping.  We will need 30 groups of 12 ounces.

30 x 12  = 360 ounces.

You will need 360 ounces of juice.