Work out the perimeter of the following triangles.

To solve the problem of finding the perimeter of each triangle, we need to add up the lengths of all three sides of each triangle. The perimeter \( P \) of a triangle is given by:

\[
P = \text{side}_1 + \text{side}_2 + \text{side}_3
\]

Let's calculate the perimeter for each triangle step by step.

Triangle 1:

- Sides: 4 cm, 2 cm, 4.5 cm
- Perimeter:
\[
P = 4 + 2 + 4.5 = 10.5 \, \text{cm}
\]

Triangle 2:

- Sides: 3 cm, 6 cm, 6.5 cm
- Perimeter:
\[
P = 3 + 6 + 6.5 = 15.5 \, \text{cm}
\]

Triangle 3:

- Sides: 3 cm, 3 cm, 4.2 cm
- Perimeter:
\[
P = 3 + 3 + 4.2 = 10.2 \, \text{cm}
\]

Triangle 4:

- Sides: 6 cm, 2 cm, 6.3 cm
- Perimeter:
\[
P = 6 + 2 + 6.3 = 14.3 \, \text{cm}
\]

Triangle 5:

- Sides: 2 cm, 6 cm, 6.3 cm
- Perimeter:
\[
P = 2 + 6 + 6.3 = 14.3 \, \text{cm}
\]

Triangle 6:

- Sides: 4 cm, 5 cm, 6.4 cm
- Perimeter:
\[
P = 4 + 5 + 6.4 = 15.4 \, \text{cm}
\]

Final Answers:

\[
\boxed{10.5, 15.5, 10.2, 14.3, 14.3, 15.4}
\]