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The Perimeter of Noncircular Shapes Practice Questions

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Updated on Oct 3, 2011

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

The Perimeter of Noncircular Shapes Practice Questions

Practice

  1. Find the perimeter

    Perimeter

  2. Find the perimeter

    Perimeter

  3. Find the perimeter

    Perimeter

Solutions

  1. 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.
  2. 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: 7x– 4 = 3x + 18

    Subtract 3x from both sides: 7x – 4 – 3x = 3x + 18 – 3x

    Combine like terms: 4x – 4 = 18

    Add 4 to both sides: 4x – 4 + 4 = 18 + 4

    Combine like terms: 4x = 22

    Divide both sides by 4:   x = 5.5

    Use this value to find the length of : 3x + 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.

  3. 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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