Answer:
15 pounds of plaster
Explanation:
First, convert ounces to pounds.
In 1 pound, there are 16 ounces. Create a proportion to convert 12 ounces to pounds.
=
![(x)/(12)](https://img.qammunity.org/2022/formulas/mathematics/high-school/s44e5nmv1rql5drdby3dg89w0vqo9whz2v.png)
Cross multiply and solve for x:
16x = 12
x = 0.75
So, each student will need 0.75 pounds of plaster. Multiply this by 20 to find the total amount the teacher will need:
20(0.75)
= 15
So, the teacher will need 15 pounds of plaster