Lesson 5

Buildings and Problems

Est. Class Sessions: 2

Developing the Lesson

Construct Buildings Given the Floor Plans and the Volumes. Show students the building you prepared prior to the lesson. See Materials Preparation and Figure 1. As a class, make a building plan for this building. First decide what the floor plan, or outline of the first floor, will be. Ask students to tell you what the difference is between a floor plan and a building plan. The building plan indicates the height, while the floor plan does not. The floor plan for this building will be 2 squares long from front to back and 3 squares long from left to right. Draw and shade that outline on a display of the Building Plan Two Ways Master from Lesson 4. See Figure 2.

  • How can you show the height of the building? (By placing a "4" in each of the six squares, the building plan is completed.)

Remind students that the height of a building is the height of the tallest column. In this case, all the columns are the same height. This is not always the case.

Ask two or three students to come to the front of the room. Ask them to pretend that they are flying over the building.

  • What do you see? Describe it to the class. (From this point of view, cubes look like squares, and all that is seen is the outline of the building, or its floor plan.)
  • Describe the floor plan for Question 1. (It is 2 squares long from left to right and 2 squares long from front to back.)

The four squares on the floor plan show the shape of the bottom layer of the building that the students will build. For Question 1A, students' buildings will have a base that is a two-by-two square. Ask student pairs to work on the problem. Question 1A has more than one solution. Some solutions are shown in Figure 3.

  • Are all the buildings the same? How are they similar? How are they different? (They all have the same first floor, and they all have the same volume. The heights are different. The shapes are different.)
  • What is the volume of the building you just built? (9 cubic units)
  • Is the volume of your building different from your neighbor's? (No, they should all be the same.)
  • What does the tallest building look like?

Have a student show his or her building and draw the corresponding building plan. See Figure 3.

  • Is there more than one way to make the tallest building? (They can have different floor plans.)
  • Are they the same shape or different? How do you know? (They are all the same shape. I can turn them to see that.)

To match the floor plan in Question 1A and use 9 cubes, the tallest building must have a column of six cubes and one cube in each of the other three columns as shown in Figure 4. Students can draw four different floor plans that match the clues. However, the shapes of all four buildings are the same.

  • What does the shortest building look like?

Have a student show his or her building and draw the corresponding building plan. See the top row of examples in Figure 3.

  • Is there more than one way to make the shortest building? How do you know? (One way is to have one column with 3 cubes and three columns with 2 cubes. Another way is to have two columns with 3 cubes, one column with 2 cubes, and one column with 1 cube.)

Ask students to complete the remaining problems on the Building Problems page. After each problem, have students analyze the different solutions and share their observations with the class.

Use Clues to Construct a Building. Remind students of Math Practices Expectation 1, Know the problem. It tells students to read problems carefully so that they know what information is important to solving a problem. In the next set of problems, students are to carefully read a list of clues.

The students will construct buildings based on the following clues:

  • the shape of the floor plan
  • the volume of the building
  • the height of the building

Read the first problem on the More Building Problems pages in the Student Activity Book with the class. The first clue is that the floor plan is a square with each side 2 units long.

  • What does it mean to say the floor plan is a square with each side 2 units long?
  • How long is the building from left to right? (2 units long)
  • How long is the building from front to back? (2 units long)
  • What is the total number of cubes on the first layer of the building? (4 cubes)
  • What is the volume of the first layer of the building? (4 cubic units)
  • What is the next clue? What does it mean for the volume to be 8 cubic units? (We can use only 8 cubes to construct the building. Each cube has a volume of 1 cubic unit.)
  • What does it mean for the height to be 2 units? (The tallest part of the building can be only 2 units high.)

Ask students to construct the buildings in Questions 1–4 and record their work. After they complete their buildings, ask students to compare their work with a neighbor.

  • How many different ways are there to construct a building for Question 1? Why? (Only one way; Since the building can be only 2 cubes high and has a volume of 8 cubic units, there is only one way.)
  • How many different ways are there to construct a building for Question 2? Why? (More than one way. Two cubes on the second "floor" can be together, or can be on a diagonal.)
  • How many different ways are there to construct a building for Question 3? Why? (This building is impossible to construct because the tallest height is 2 units. There is an extra cube that we cannot use.)
  • How many different ways are there to construct a building for Question 4? Why? (There are many solutions. We can use a lot of cubes so there are a lot of possibilities.)

Students make up their own building problem in Question 5. When students have completed the problems, ask two or three to show their buildings and have the rest of the class construct a building with their clues.

  • Is there more than one way to construct this building? Why or why not?

For more of a challenge, ask students who have completed Question 5 to:

  • construct a building that matches the clues, but is different from the one they just constructed.
  • compare their solution with a neighbor. How are the solutions similar? How are they different?
  • make a building plan for their neighbor's building.
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Display building with 24 cubic units
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A floor plan for the sample building does not indicate height
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Plans for buildings with a volume of 9 cubic units
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Building plans for buildings with heights of 6 units and volumes of 9 cubic units
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