Cubes: Finding a diagonal - using the Pythagorean theorem

Shown below is a cube with edges equal to 2 cm.

What is the length of the diagonal of the cube's face shown in the figure?

$2\times\sqrt{2}$ cm

Shown below is a cube with edges equaling 5 cm.

What is the length of the diagonal on the cube's face?

$5\times\sqrt{2}$ cm

Below is a cube with edges equal to 4 cm.

What is the length of the diagonal of the cube's face indicated in the figure?

$4\times\sqrt{2}$ cm

Shown below is a cube with edges that equal 6 cm.

What is the length of the inner diagonal of the cube?

$10.39$ cm

Shown below is a cube with edges equal to 10 cm.

What is the length of the inner diagonal of the cube?

$17.3$ cm