Lesson+3+-+Areas+of+Triangles

= Lesson #3 =

Title of lesson: Areas of Triangles
Description of lesson: Students will use what they've learned so far about finding the areas of rectangles and parallelograms to find the areas of triangles. Triangles can be doubled to form rectangles and parallelograms, so the students will use what they've learned so far not only to find the area of a triangle, but to understand the area formula that we typically use to find the area of a triangle.

Assignment: We will work as a large group, in small groups and individually to solve for the areas of various triangles. We'll begin the lesson with a warm-up problem where students will work individually to find the area of a parallelogram using what they learned in the previous lesson. After the students have been given 5 minutes to work individually, we will take 5 minutes to discuss the solution as a class.

A paralellogram will be displayed on the smartboard/promethean board and we will work as a group to solve for its area. Once we've found the area of the parallelogram, we will work together to split the parallelogram into two triangles and prove, using SSS that the triangles are congruent. Then we can show that each triangle's area is half the total area of the parallelogram. This should take approximately 10 minutes. Another parallelogram will then be displayed on the board and the students will be divided into groups of 3-4 and asked to solve for the area, divide the parallelogram into two triangles, and find the area of each triangle. They will be given 10 minutes to work on this. After the students have had time to work in their groups, we will spend about 5 minutes discussing the solution as a class. A triangle will then be displayed on the board and the students will be shown the area formula for finding the area of a triangle (A = half the base times the height) and how it relates to the way we found the area of a parallelogram and split it into two congruent triangles. We will then solve for the area of the triangle using the area formula.

For homework, the students will be assigned a short worksheet of practice problems and asked to blog about the lesson: what they understood, what they didn't understand, what they thought could have been done differently, etc.

Resources/materials needed: Students may use the textbook as an additional reference. We will be using the smartboard/promethean board during class and students will need to bring their notebooks, and a pencil. The worksheet will be posted on the class website along with review flashcards for the lesson:

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Technology reflection: The flashcards for the lesson will reinforce learning. The flashcards will provide the formulas and definitions used in class so that students can use them for their homework. They will also provide parents with a source for information if they'd like to check or help with the students' homework.

Evaluation: I will need to focus on making sure all of the students' needs are met by the lesson and that no one is being left behind. I will need to make sure I keep on track in terms of timing so that we are able to cover the unit in the time allotted. I will also need to make sure I have a backup plan in place just in case there is a technical problem with any of the technology. For example, I'll need to make sure I have chalk or dry erase markers in case the smartboard/promethean board isn't working. I'll also need to make sure I have a few copies of the homework printed in case there are any problems with the class website or there are students who can't access the internet for some reason.