The cube has 6 square 8.5×8.5 sides, or faces:
1. A front side, or 8.5×8.5=72.5 square inch front side face
2. A back side, or 8.5×8.5=72.5 square inch back side face
3. A left side, or 8.5×8.5=72.5 square inch left side face
4. A right side, 8.5×8.5=72.5 square inch or right side face
5. A top side, or 8.5×8.5=72.5 square inch top side face
6. A bottom side, or 8.5×8.5=72.5 square inch side face face
So we multiply 72.5 square inches by 6 and get that 433.5
square inches of wrapping paper would cover the box completely
without overlapping.
Edwin