To review the concept of perimeter, go to The Perimeter of Noncircular Shapes Study Guide.

**The Perimeter of Noncircular Shapes Practice Questions**

**Practice**

- Find the perimeter
- Find the perimeter
- Find the perimeter

**Solutions**

- Add up the lengths of all sides, that is,
*AB, BC*, and*AC*. The height, 3 mm, is information that is not needed to calculate the perimeter. Substitute into get 6 + 4 + 5 = 15 millimeters. -
In a rectangle, like all parallelograms, the opposite sides are parallel and congruent. In this example, . Use algebra to solve for the variable

*x*.Set up an equation: 7

*x*– 4 = 3*x*+ 18Subtract 3

*x*from both sides: 7*x*– 4 – 3*x*= 3*x*+ 18 – 3*x*Combine like terms: 4

*x*– 4 = 18Add 4 to both sides: 4

*x*– 4 + 4 = 18 + 4Combine like terms: 4

*x*= 22Divide both sides by 4:

*x*= 5.5Use this value to find the length of : 3

*x*+ 18 = (3 × 5.5) + 18 = 34.5. Use the shortcut for the perimeter of a rectangle:*P*= (2 × 34.5) + (2 × 27.3) = 69 + 54.6 = 123.6 inches. - To find perimeter, you add up all the lengths of the sides of the polygon. The perimeter is 7.4 + 6 + 2.2 + 8 = 23.6 feet.

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