# Surface Area of a Triangular Prism - What shape is the base?

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## Objective

Students will be able to make connections to prior learning of surface area of a rectangular prism, which allows them to develop of a method for finding surface area of a triangular prism on their own.

#### Big Idea

Students make connections to prior learning of surface area of a rectangular prism, which allows them to develop of a method for finding surface area of a triangular prism on their own.

## Launch

10 minutes

OpenerAs students enter the room, they will immediately pick up and begin working on the opener – Instructional Strategy - Process for openers.  This method of working and going over the opener lends itself to allow students to construct viable arguments and critique the reasoning of others, which is mathematical practice 3.

Learning Target: After completion of the opener, I will address the day’s learning targets to the students.  In today’s lesson, the intended target is “I can calculate the surface area of a triangular prism.”

## Explore

45 minutes

Brainstorm: Students will brainstorm how to calculate the surface area of a triangular prism, based on their prior knowledge (MP 1).  They will have 3 minutes to discuss with their table groups.  I will open the floor for discussion regarding how the students think we should approach the problem, and I will ask for a show of hands for who worked it out and got an answer of 214 in2.  I will work out this same problem for their notes example.

Surface Area of a Triangular Prism Notes: After the discussion, I will go into instruction on finding the surface area of a triangular prism.  I will ask students to add the information to their foldable as well as their guided notes sheet.  I will walk the students through finding the surface area by identifying the sides and their dimensions.  Included in our discussion will be the formula for finding the area of the base – stressing that in triangles one must divide by 2, and the number of faces/bases that form a triangular prism.  I will work out the two class examples using student input.

Table Practice: After the class examples, the students will work on 4 table practice problems.  For each problem, I ask that they draw out the decomposed figure – 2 triangles, and 3 rectangles, labeling each with its dimensions.  I will walk around and provide assistance as needed, and then I will take volunteers to work the problems at the board. It is important that when students work with these figures, they pay close attention to precision (MP 6) - did they include all of the sides? Did they use the correct 2D area formulas? Do they have the right units? Higher level students will make connections and derive formulas on their own (MP 7 and 8) for the triangular prism, however, at this age level I do not explicitely cover the formula.

## Summarize + Homework

5 minutes

Table Discussion: To summarize the lesson, I will ask students to turn to their shoulder buddy at their table, and discuss the differences between calculating surface area of a triangular prism and rectangular prism. I am hoping to hear students discuss the formulas for finding areas of the bases as well as the differing numbers of faces/bases on each figure. Based on my observation of conversations, I will ask a few students to share out. Summary Thoughts

HomeworkWith any remaining time in class, students will be asked to begin their homework. On this particular homework, I have given them the answers, and I ask that they show me all the work that leads up to those answers. That way, they know if they are on the right track. Philosophy on Homework