1. **State the problem:** Find the perimeter of a triangle with sides 6 cm, 6 cm, and 9 cm.
2. **Formula:** The perimeter $P$ of a triangle is the sum of the lengths of its three sides.
$$P = a + b + c$$
where $a$, $b$, and $c$ are the side lengths.
3. **Substitute the given values:**
$$P = 6 + 6 + 9$$
4. **Calculate the sum:**
$$P = 21$$
5. **Answer:** The perimeter of the triangle is 21 cm.
Triangle Perimeter 6Ef1B4
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