The diagram shows a cuboid. On the 1 cm² grid, complete the net of the cuboid. One face has been drawn for you. A cube has a surface area of 384 cm². Find the length of one of its sides.

The missing face is the back face, which is a $6 \text{ cm} \times 3 \text{ cm}$ rectangle.

To complete the net, draw the final $6 \text{ cm} \times 3 \text{ cm}$ rectangle. A common way to attach it is to the $6 \text{ cm}$ edge of the $6 \text{ cm} \times 2 \text{ cm}$ face that is positioned above the central $6 \text{ cm} \times 3 \text{ cm}$ face. This means extending the net upwards from the top face.

(Since I cannot draw on the image, I am describing the completion of the net based on the visible drawing.)

20. (b) A cube has a surface area of 384 cm². Find the length of one of its sides.

The surface area $A$ of a cube with side length $s$ is given by $A = 6s^2$, because a cube has 6 identical square faces.

We are given $A = 384 \text{ cm}^2$.

Divide both sides by 6:

Take the square root of both sides:

The length of one of its sides is $\boxed{8 \text{ cm}}$.