Each student in a class needs 12 ounces of plaster for a project, and there are 20 students. How many pounds of plaster will the teacher need?

To find out how many pounds of plaster the teacher needs for the class, start by calculating the total amount of plaster required in ounces. Each student needs 12 ounces, and there are 20 students. Therefore, multiply the number of students by the amount of plaster each one requires:

12 ounces per student × 20 students = 240 ounces.

Next, to convert ounces into pounds, it's important to know that there are 16 ounces in a pound. Thus, divide the total number of ounces by 16 to find the total weight in pounds:

240 ounces ÷ 16 ounces per pound = 15 pounds.

This calculation shows that the teacher will need a total of 15 pounds of plaster for the project.