How do you calculate the surface area of a cube with side length 3 cm?

The surface area of a cube with side length 3 cm is 54 cm².

To calculate the surface area of a cube, you need to know the length of one of its sides. A cube has six faces, and each face is a square. The formula for the area of a square is side length squared. So, if the side length of the cube is 3 cm, the area of one face is \(3 \, \text{cm} \times 3 \, \text{cm} = 9 \, \text{cm}^2\).

Since a cube has six identical faces, you multiply the area of one face by 6 to get the total surface area. Therefore, the surface area of the cube is \(6 \times 9 \, \text{cm}^2 = 54 \, \text{cm}^2\).

In summary, the steps are:
1. Find the area of one face: \(3 \, \text{cm} \times 3 \, \text{cm} = 9 \, \text{cm}^2\).
2. Multiply by the number of faces: \(6 \times 9 \, \text{cm}^2 = 54 \, \text{cm}^2\).

This method works for any cube, regardless of the side length. Just remember to square the side length to find the area of one face and then multiply by six to get the total surface area.