Find the perimeter of a triangle that has the side lengths of 2cm, 6cm and 9cm.

The picture below shows the triangle:

We start with the formula for the perimeter of a triangle, P, as shown below.

Now, this formula simply means that we can find its perimeter by adding up all the side lengths together. Hence, we have:

It is important to include the unit. Since, the sides lengths are given in cm, P will be in cm:

Therefore, the answer is A.

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