Lesson 23 NYS COMMON CORE MATHEMATICS CURRICULUM 7•6 Lesson 23: Surface Area Student Outcomes ο§ Students determine the surface area of three-dimensional figures, including both composite figures and those missing sections. Lesson Notes This lesson is an extension of the work done on surface area in Module 5 of Grade 6 (Lessons 15–19) as well as Module 3 of Grade 7 (Lessons 21–22). Scaffolding: Classwork Encourage students that are struggling to draw a net of the figure to help them determine the surface area. Opening Exercise (5 minutes) Opening Exercise Calculate the surface area of the square pyramid. Area of the square base: ππ Area of the triangular lateral sides: π π ππ π (π ππ)(π ππ) π = ππ πππ = There are four lateral sides. So the area of all π triangles is ππ πππ. MP.1 Surface Area: π (π ππ β π ππ) + π ( (π ππ β π ππ)) = ππ πππ + ππ πππ π = πππ πππ ο§ Explain the process you used to determine the surface area of the pyramid. οΊ Answers will vary. Students may have drawn a net or determined the area of each side without the net. Emphasize how each method determines the area of the sides and then adds them together. ο§ The surface area of a pyramid is the union of its base region and all its lateral faces. ο§ Explain how (8 ππ β 8 ππ) + 4 ( (8 ππ β 5 ππ)) represents the surface area. 1 2 οΊ The area of the square with side lengths of 8 ππ is represented by (8 ππ β 8 ππ), and the area of the 1 four lateral faces with base lengths of 8 ππ and heights of 5 ππ is represented by 4 ( (8 ππ β 5 ππ)). 2 ο§ Would this method work for any prism or pyramid? MP.1 Lesson 23: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Surface Area 4/13/20 246 This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Lesson 23 NYS COMMON CORE MATHEMATICS CURRICULUM οΊ 7•6 Answers will vary. Students should come to the conclusion that calculating the area of each lateral face will determine the surface area even if the areas are determined in different orders, by using a formula or net, or any other method. Example 1 (10 minutes) Students find the surface area of the rectangular prism. Then students will determine the surface area of the rectangular prism when it is broken into two separate pieces. Finally, students will compare the surface areas before and after the split. Scaffolding: Students may benefit from a physical demonstration of this, perhaps using base ten blocks. Example 1 a. Calculate the surface area of the rectangular prism. Surface Area: π(π ππ.× π ππ. ) + π(π ππ.× ππ ππ. ) + π(π ππ.× ππ ππ. ) = π(ππ πππ ) + π(ππ πππ ) + π(ππ πππ ) = ππ πππ + ππ πππ + πππ πππ = πππ πππ MP.3 Have students predict in writing or in discussion with a partner whether or not the sum of the two surface areas in part (b) will be the same as the surface area in part (a). b. Imagine that a piece of the rectangular prism is removed. Determine the surface area of both pieces. The surface area of the shape on the left: Area for front and back sides: π (π ππ. × π ππ. ) = π(ππ πππ ) = ππ πππ Area for front and back sides: π(π ππ.× π ππ. ) = π(π πππ ) = ππ πππ Area seen from left and right: π(π ππ.× ππ ππ. ) = π(ππ πππ ) = ππ πππ Area for left and right sides: π(π ππ.× π ππ. ) = π(ππ πππ ) = ππ πππ Area for top and bottom: π(π ππ.× π ππ. ) = π(ππ πππ ) = ππ πππ Area of extra sides: Area of top and bottom: Surface area: ο§ The surface area of the shape on the right: π(π ππ.× π ππ. ) = π(π πππ ) = ππ πππ π(π ππ.× ππ) − π(π ππ.× π ππ. ) = π(ππ πππ ) − π(ππ πππ ) = πππ πππ − ππ πππ = πππ πππ Surface area: π πππ + ππ πππ + ππ πππ = ππ πππ ππ πππ + ππ πππ + ππ πππ + πππ πππ = πππ ππ.π How did you determine the surface area of the shape on the left? Lesson 23: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Surface Area 4/13/20 247 This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Lesson 23 NYS COMMON CORE MATHEMATICS CURRICULUM οΊ 7•6 I was able to calculate the area of the sides that are rectangles using length times width. For the two bases that are C-shaped, I used the area of the original top and bottom and subtracted the piece that was taken off. c. How is the surface area in part (a) related to the surface area in part (b)? If I add the surface area of both figures, I will get more than the surface area of the original shape. πππ πππ + ππ πππ = πππ πππ πππ πππ − πππ πππ = ππ πππ ππ πππ is twice the area of the region where the two pieces fit together. There are ππ more square inches when the prisms are separated. Exercises 1–5 (18 minutes) Exercises 1–5 Determine the surface area of the right prisms. 1. Area of top and bottom: π π π ( (ππ ππ.× π ππ. )) = ππ ππ.× π ππ. = πππ πππ Area for front: ππ ππ.× ππ ππ. = πππ πππ Area that can be seen from left: ππ ππ.× ππ ππ. = πππ πππ Area that can be seen from right: π ππ.× ππ ππ. = πππ πππ Surface area: πππ πππ + πππ πππ + πππ πππ + πππ πππ = πππ πππ 2. Area of front and back: π π π ( (ππ ππ . + π ππ . )πππ . ) = ππ ππ .× π ππ . = ππ ππ π Area of top: Area that can be seen from left and right: π ππ .× ππ ππ . = ππ ππ π π(π ππ .× ππ ππ . ) = π(ππ ππ .π ) = πππ ππ π Area of bottom: ππ ππ .× ππ ππ . = πππ ππ π Surface area: ππ ππ π + ππ ππ π + πππ ππ π + πππ ππ π = πππ ππ π 3. Area of top and bottom: π ((π ππ.× π ππ. ) + (π ππ × π ππ. )) = π(ππ πππ + ππ πππ ) = π(ππ πππ ) = πππ πππ Lesson 23: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Surface Area 4/13/20 Area for back: π ππ.× π ππ. = ππ πππ Area for front: π ππ.× π ππ. = ππ πππ Area of corner cut out: 248 π (π ππ.× π ππ. ) + (πunder ππ.×a π ππ. ) = π ππ This work is licensed Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Area of right side: π ππ.× π ππ. = ππ πππ Area of left side: π ππ.× π ππ. = ππ πππ Lesson 23 NYS COMMON CORE MATHEMATICS CURRICULUM 7•6 Surface area: πππ πππ + ππ πππ + ππ πππ + π πππ + ππ πππ + ππ πππ = πππ πππ 4. Surface area of top prism: Area of top: π π × π π = ππ ππ Area of front and back sides: π(π π × π π) = ππππ Area of left and right sides: π(π π × π π) = ππ ππ Surface area of bottom prism: Area of top: ππ π × ππ π − ππ ππ = ππ ππ Area of bottom: ππ π × ππ π = πππ ππ Area of front and back sides: π(ππ π × π π) = ππ ππ Area of left and right sides: π(ππ π × π π) = ππ ππ Surface area: πππ ππ + πππ ππ = πππ ππ 5. Area of top and bottom faces: Area of lateral faces: π(ππ ππ.× π ππ. ) + π(π ππ.× π ππ. ) = ππ πππ + ππ πππ = ππ πππ π(π ππ.× π ππ. ) + π(π ππ.× π ππ. ) = ππ πππ + πππ πππ + π(ππ ππ.× π ππ. ) = πππ πππ Surface area: ππ πππ + πππ πππ + πππ πππ = πππ πππ Closing (2 minutes) ο§ Describe the process you use to find the surface area of shapes that are composite figures or that are missing sections. οΊ To determine the surface area of a right prism, find the area of each lateral face and the two base faces, then add the areas of all the faces together. Exit Ticket (10 minutes) Lesson 23: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Surface Area 4/13/20 249 This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Lesson 23 NYS COMMON CORE MATHEMATICS CURRICULUM Name 7•6 Date Lesson 23: Surface Area Exit Ticket Determine and explain how to find the surface area of the following right prisms. 1. 2. Lesson 23: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Surface Area 4/13/20 250 This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Lesson 23 NYS COMMON CORE MATHEMATICS CURRICULUM 7•6 Exit Ticket Sample Solutions Determine and explain how to find the surface area of the following right prisms. 1. Area of top and bottom: π π ( (ππ ππ.× π ππ. )) π = ππ ππ.× π ππ. = ππ πππ Area of front: ππ ππ.× ππ ππ. = πππ πππ Area seen from left: ππ ππ.× ππ ππ. = πππ πππ Area seen from right: π ππ.× ππ ππ. = ππ πππ Surface Area: ππ πππ + πππ πππ + πππ πππ + ππ πππ = πππ πππ To find the surface area of the triangular prism, I must sum the areas of two triangles (the bases that are equal in area) and the areas of three different sized rectangles. 2. Area of front and back: Area of sides: Area of top and bottom: π(ππππ.× π ππ. ) = ππ πππ π(ππ ππ.× π ππ. ) = ππ πππ π(ππ ππ.× π ππ. ) + π( π ππ.× π ππ. ) = πππ πππ + ππ πππ = πππ πππ Surface Area: ππ πππ + ππ πππ + πππ πππ = πππ πππ To find the surface area of the prism, I must sum the composite area of the bases with rectangular areas of the sides of the prism. Lesson 23: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Surface Area 4/13/20 251 This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Lesson 23 NYS COMMON CORE MATHEMATICS CURRICULUM 7•6 Problem Set Sample Solutions Determine the surface area of the figures. 1. Area of top and bottom: π(π ππ × π ππ) = ππ πππ Area of left and right sides: π(π ππ × π ππ) = ππ πππ Area of front and back: π(π ππ × π ππ) + π(π. π ππ × π ππ) = πππ πππ Surface area: ππ πππ + ππ πππ + πππ πππ = πππ πππ 2. Area of front and back: π(π ππ × π ππ) = ππ πππ Area of sides: π(π ππ × π ππ) = ππ πππ Area of top and bottom: π(π ππ × π ππ) − π( π ππ × π ππ) = πππ πππ − ππ πππ = πππ πππ Surface area: ππ πππ + ππ πππ + πππ πππ = πππ πππ Surface Area of Top Prism: 3. Area of top: π ππ.× π ππ. = ππ πππ Area of front and back sides: π(π ππ.× π ππ. ) = πππππ Area of left and right sides: π(π ππ.× π ππ. ) = πππ πππ Surface Area of Bottom Prism: Area of top: Area of bottom: ππ ππ.× ππ ππ. − ππ πππ = πππ πππ ππ ππ.× ππ ππ. = πππ πππ Area of front and back sides: π(ππ ππ.× π ππ. ) = πππ πππ Area of left and right sides: π(ππ ππ.× π ππ. ) = πππ πππ Surface area: πππ πππ + πππ πππ = πππ πππ Lesson 23: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Surface Area 4/13/20 252 This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Lesson 23 NYS COMMON CORE MATHEMATICS CURRICULUM 7•6 4. Area of the rectangle base: ππ ππ.× ππ ππ. = πππ πππ Area of the triangular lateral sides: Area of front and back: π ππ π π = π ( (ππ ππ. )(ππ ππ. )) π = πππ πππ Area that can be seen from left and right: π ππ π π = π ( (ππ ππ. )(ππ ππ. )) π = πππ πππ Surface area: πππ πππ + πππ πππ + πππ πππ = ππππ πππ 5. Area of front and back: π π ( (π ππ × ππ ππ)) π = π ππ × ππ ππ = πππ πππ Area of bottom: π ππ × ππ ππ = πππ πππ Area that can be seen from left side: Area that can be seen from right side: ππ ππ × ππ ππ = πππ πππ ππ ππ × ππ ππ = πππ πππ Surface area: πππ πππ + πππ πππ + πππ πππ + πππ πππ = π, πππ πππ Lesson 23: Date: © 2014 Common Core, Inc. Some rights reserved. commoncore.org Surface Area 4/13/20 253 This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.