Parallelogram Side Length: Finding CD When Perimeter is 22cm and AB = 8cm

To solve this problem, we need to calculate the length of side $CD$ given the perimeter and one side length.

Step 1: Identify the given information. We know that the perimeter $P$ of the parallelogram is 22 cm, and one of the sides, $AB$, is 8 cm.

Step 2: Apply the perimeter formula for a parallelogram, which states that $P = 2(AB + BC)$. Since $AB = CD$ and $BC = DA$ (opposite sides are equal), we have:

$22 = 2(8 + CD)$.

Step 3: Solve for $CD$. First, simplify the equation:

$22 = 2(8 + CD)$.

$22 = 16 + 2 \cdot CD$.

$22 - 16 = 2 \cdot CD$.

$6 = 2 \cdot CD$.

Divide both sides by 2 to find $CD$:

$CD = \frac{6}{2} = 3$ cm.

Therefore, the length of side $CD$ is $3$ cm, which corresponds to choice 1.