Lesson plan

# 10. Find unknown measures in triangles (A)

teaches Common Core State Standards CCSS.Math.Content.7.G.A.2 http://corestandards.org/Math/Content/7/G/A/2
teaches Common Core State Standards CCSS.Math.Content.7.G.B.5 http://corestandards.org/Math/Content/7/G/B/5
teaches Common Core State Standards CCSS.Math.Practice.MP3 http://corestandards.org/Math/Practice/MP3
teaches Common Core State Standards CCSS.Math.Practice.MP5 http://corestandards.org/Math/Practice/MP5
teaches Common Core State Standards CCSS.Math.Practice.MP7 http://corestandards.org/Math/Practice/MP7

## You have saved this lesson plan!

Here's where you can access your saved items.

Dismiss

You'll gain access to interventions, extensions, task implementation guides, and more for this lesson plan.

Lesson objective: Apply their understanding of the Triangle Inequality Theorem to determine an efficient design for a kitchen.

This lesson provides an opportunity for students to apply their knowledge and understanding the the sum of any two lengths of a triangle must be greater than the length of the third side to a real-life situation. Students are asked to consider three possible locations for a stove in a kitchen so that an efficient "kitchen work triangle" can be formed.

Key Concept students will use:

• The sum of the lengths of two sides of a triangle must be greater than the length of the third side, and this can be informally proven.

Skills students will use:

• the Triangle Inequality Theorem to decide an unknown measure, the distance from the sink to the stove in a kitchen.
• when given two sides of a triangle, students will determine the range of acceptable values for the length of the third side of the triangle.

Students engage in Mathematical Practice #3 (construct viable arguments and critique the reasoning of others) as they decide the best location for a stove that will produce the most efficient design for a kitchen.​

Key vocabulary:

• acute triangle
• angle
• base angle
• isosceles triangle
• obtuse triangle
• right triangle
• side
• triangle angle sum
• Triangle Inequality Theorem

Special materials needed:

• protractor
• ruler