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Home > CC1 > Chapter 1 > Lesson 1.1.3 > Problem 1-21


Find the perimeter of each figure below. The markings on part (b) mean that the lines are parallel. The markings on part (e) show that all sides are the same length. As you find each perimeter, be sure to show your work. Homework Help ✎

  1. 1-21a Rectangle 90 degree marks on all corners 8 cm by 3 cm.

  • This shape is a rectangle. Find its perimeter. Remember that the perimeter is the total length of the border around the shape.

  • Find the unknown lengths and label them on your diagram. Now try to find the perimeter without looking at the answer.

  • Be sure to show why the perimeter is cm.

  1. 1-21b. Trapezoid top 5 cm. base 9 cm. Arrows showing the top and base are parallel. Each of the diagonal sides are 3 cm.

  • The perimeter is the total length of the border around the shape.

    The perimeter is . Calculate this sum.

    . Can you show how you arrived at this answer?

  1. 1-21c. Right triangle as indicated by the square in the lower right corner. The base is 5 in. the vertical leg is 12 in. The hypotenuse is 13 in.

    See (a) and (b).

  1. 1-21d. A triangle with sides 6mm, 4mm, and 3mm.

    See (a) and (b).

  1. 1-21e. A quadrilateral with tick marks showing all side are equal and are 4 ft.

    The markings mean that all the sides are long.

  1. 1-21f. A triangle with the base at 5m. The two other sides are both 10m.

  • See (a) and (b).