Adisplay number cube measures 20 inches on a side. the sides are numbered 1-6. the odd-numbered sides are covered in blue fabric and the even-numbered sides are covered in red fabric. how much red fabric was used?

To find the amount of fabric used on red fabric (the even numbered sides), you will need to find the surface area of 3 out of the 6 faces.  They are all cube, so when you find the area of one face, you have the area of all of them!

To find the area of one of the faces you will multiply the length of the edge by itself.  In this case, 20 in. by 20 in.

20 x 20 = 400 square inches per face.

400 square inches x 3 red faces = 1200 square inches 

You will need 1200 square inches of red fabric to cover the even numbered sides of the cube.