Lesson 14 Find the Area of Figures with Missing Sides

    • Let’s find the area of figures with missing side lengths.

Warm-up Notice and Wonder: Mystery Sides

What do you notice? What do you wonder?

6-sided shape.

Activity 1 The Mystery Side

Tyler says that the missing side length is 5 meters because it looks longer than the sides that are 4 meters long.

Do you agree or disagree? Be prepared to explain your reasoning.

6-sided shape. Straight sides. All side lengths meet at right angles: Bottom, 4 m. Right side rises 12 m,  goes left 8 m, down 6 m, right 4 m, down question mark m.

Activity 2 Practice with Mystery Sides

Find the area of each figure. Explain or show your reasoning.

  1. Long description: 6-sided shape. Straight sides. All side lengths meet at right angles. Side lengths: Bottom, 4 m. Right side rises 12 m, then goes left 8 m, and down 6 m, left 4 m, and down question mark m.
  2. 8-sided shape.

Practice Problem

Problem 1

Find the area of this figure. Explain or show your reasoning.

6-sided shape. Straight sides. All side lengths meet at right angles. Bottom, question mark feet. Right side rises question mark feet then goes left 5 feet, then down 2 feet and left 3 feet. Left side 8 feet.