There are 6 faces of a cube. If Matthew painted half of the faces red, then find the surface area (SA= 2(LW+WH+ HL) of all the faces and divide it by two. You will end up with the total of 486 before you divide. After you divide, you will end up with 243 as the surface area Matthew painted red.
*The formula SA=2(LW+WH+HL)
L is length, W is width, and H is height.