Solid Shapes - 9.3 | 9. Mensuration | CBSE 8 Mathematics | Allrounder.ai
K12 Students

Academics

AI-Powered learning for Grades 8–12, aligned with major Indian and international curricula.

Professionals

Professional Courses

Industry-relevant training in Business, Technology, and Design to help professionals and graduates upskill for real-world careers.

Games

Interactive Games

Fun, engaging games to boost memory, math fluency, typing speed, and English skills—perfect for learners of all ages.

Interactive Audio Lesson

Listen to a student-teacher conversation explaining the topic in a relatable way.

Introduction to Solid Shapes

Unlock Audio Lesson

Signup and Enroll to the course for listening the Audio Lesson

0:00
Teacher
Teacher

Today, we will learn about solid shapes! Can anyone tell me what shapes are considered solid?

Student 1
Student 1

Are cuboids and cylinders solid shapes?

Teacher
Teacher

Exactly! Solid shapes occupy space and have three dimensions: length, breadth, and height. What can you tell me about cuboids?

Student 2
Student 2

Cuboids have six rectangular faces.

Teacher
Teacher

Right! And remember that they have three pairs of identical faces. Let’s always think of the acronym 'CUBES': Congruent Faces, Uniform Dimensions, Box Shape, Essential for calculation, Solid.

Student 3
Student 3

What about cubes? Are they different?

Teacher
Teacher

Great question! Cubes are a special kind of cuboid where all six faces are square. That's why cubes are always equal in length, width, and height.

Student 4
Student 4

So every side of a cube is the same?

Teacher
Teacher

Absolutely! Now, what are some examples of cuboidal shapes we see every day?

Student 1
Student 1

Boxes, buildings, and books!

Teacher
Teacher

Exactly! Let’s summarize our key points. Cuboids have rectangular faces, cubes have square faces, and both have unique properties that are crucial in our studies of volume and surface area.

Exploring Cylinders

Unlock Audio Lesson

Signup and Enroll to the course for listening the Audio Lesson

0:00
Teacher
Teacher

Now let's dive into cylinders! Who can define what a cylindrical shape looks like?

Student 2
Student 2

It has a curved surface and two circular faces, right?

Teacher
Teacher

That's correct! This is what makes a right circular cylinder distinct. Remember the mnemonic 'CCP': Curved surface, Congruent faces, and Parallel circles. What are some everyday examples of this shape?

Student 3
Student 3

Like a soda can and a pipe!

Teacher
Teacher

Exactly! Excellent examples. Can anyone explain how the circular faces relate to the height of the cylinder?

Student 4
Student 4

The height is perpendicular to the bases, connecting the top and bottom faces.

Teacher
Teacher

Well done! Let’s briefly recap: Cylinders have congruent circular bases, a curved surface, and their height connects the bases at a right angle.

Hands-On Exploration of Solid Shapes

Unlock Audio Lesson

Signup and Enroll to the course for listening the Audio Lesson

0:00
Teacher
Teacher

I hope you’re all ready for some hands-on activity! I want you to collect different boxes from home. Let's start with cuboidal shapes.

Student 1
Student 1

I found a rectangular box and a square box!

Student 2
Student 2

Me too! I also brought a cylindrical can from my kitchen.

Teacher
Teacher

Wonderful! Now, can you identify the faces? Are the faces identical?

Student 3
Student 3

The rectangular box has pairs but the cube has all identical square faces.

Teacher
Teacher

Yes! Remember to observe how many congruent faces each solid has. Let’s document our findings!

Student 4
Student 4

I noticed that the cylinder doesn’t have flat faces like the boxes.

Teacher
Teacher

Excellent observation! The curved surface of the cylinder sets it apart from the others.

Introduction & Overview

Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.

Quick Overview

This section introduces solid shapes, highlighting the differences between cuboidal, cubic, and cylindrical forms and their corresponding properties.

Standard

In this section, students explore various solid shapes, identifying key characteristics such as the number of faces, types of faces, and the congruency of faces. They learn about right circular cylinders and the physical objects that demonstrate these shapes.

Detailed

Detailed Summary

In this section, we delve into solid shapes, which are three-dimensional forms involving length, breadth, and height. Students are introduced to three primary solid shapes: cuboids, cubes, and cylinders. Each form has distinct characteristics:

  • Cuboids: All six faces are rectangular in shape, where opposite faces are identical. The number of identical faces is three pairs of rectangular faces.
  • Cubes: The special case of the cuboid with all six faces as squares, making all sides equal. Thus, only one face shape exists for cubes.
  • Cylinders: A right circular cylinder consists of one curved surface and two identical circular faces. The line segment connecting the centers of the circular faces is perpendicular to the base, indicating the shape's right circularity.

Students engage in hands-on exploration by collecting and dissecting physical examples of these boxes, deepening their understanding of solid shapes through observation of congruent and non-congruent faces. Overall, this section sets the stage for further study in surface area and volume, essential concepts in mensuration.

Youtube Videos

Mensuration - Solid Shapes- #class8 #chapter11  #tys #ncertmaths
Mensuration - Solid Shapes- #class8 #chapter11 #tys #ncertmaths
Class 8 Maths Chapter 11 | Solid Shapes - Mensuration
Class 8 Maths Chapter 11 | Solid Shapes - Mensuration
Solid Shapes - Mensuration | Class 8 Maths Chapter 9 | CBSE 2024-25
Solid Shapes - Mensuration | Class 8 Maths Chapter 9 | CBSE 2024-25
Which Shape has the Largest Area for a Fixed Perimeter? | #NowWeKnow #Shorts #BYJUS
Which Shape has the Largest Area for a Fixed Perimeter? | #NowWeKnow #Shorts #BYJUS
Class 8 Maths Chapter 11 Solid Shapes - Mensuration | NCERT Book
Class 8 Maths Chapter 11 Solid Shapes - Mensuration | NCERT Book
Area of polygons
Area of polygons
class 8 chapter 11 mensuration all formulas
class 8 chapter 11 mensuration all formulas
Volume of a cube
Volume of a cube
Total & Lateral Surface Area of Cylinder|TSA & LSA of Cylinder|Mensuration|Class 8th #mathsshorts
Total & Lateral Surface Area of Cylinder|TSA & LSA of Cylinder|Mensuration|Class 8th #mathsshorts
mensuration formula triangle rhombus circles square trapezium जानिए पूरी जानकारी
mensuration formula triangle rhombus circles square trapezium जानिए पूरी जानकारी

Audio Book

Dive deep into the subject with an immersive audiobook experience.

Introduction to Solid Shapes

Unlock Audio Book

Signup and Enroll to the course for listening the Audio Book

In your earlier classes you have studied that two dimensional figures can be identified as the faces of three dimensional shapes. Observe the solids which we have discussed so far (Fig 9.10).

Detailed Explanation

Solid shapes are three-dimensional objects that occupy space and have volume. Unlike two-dimensional shapes, which only have length and width and can be described by their perimeter or area, solid shapes have depth as well. This depth gives them volume, which is how much space they take up. Some examples of solid shapes include cubes, cuboids, cylinders, and spheres. When teaching about solid shapes, it's essential to first connect them to two-dimensional shapes by explaining that the faces of these solid shapes are actually two-dimensional figures.

Examples & Analogies

Consider the packaging of different products; a cube-shaped box can hold items just like a rectangle box can, but one is easier to store in a drawer while the other may fit better on a shelf due to its shape. It's like packing a backpack: some shapes fit better than others, depending on their dimensions.

Identical Faces in Solid Shapes

Unlock Audio Book

Signup and Enroll to the course for listening the Audio Book

Observe that some shapes have two or more than two identical (congruent) faces. Name them. Which solid has all congruent faces?

Detailed Explanation

Identical or congruent faces are those that are the same shape and size. For example, a cube has six faces that are all squares, while a cuboid has rectangular faces that can be congruent in pairs. Understanding that solid shapes can have identical faces helps students visualize and identify these shapes based on their properties. Identifying which solids have all congruent faces, like a cube, exemplifies symmetry and uniformity in geometry.

Examples & Analogies

Think of building blocks shaped like cubes. Every block looks the same, making it easy to stack and build structures. If some blocks were shaped differently, the build would be less stable and might not fit together as well.

Different Types of Boxes

Unlock Audio Book

Signup and Enroll to the course for listening the Audio Book

Soaps, toys, pastes, snacks etc. often come in the packing of cuboidal, cubical or cylindrical boxes. Collect, such boxes (Fig 9.11).

Detailed Explanation

In this chunk, the focus is shifted to practical applications of solid shapes in everyday life. Many products we use are packaged in solid shapes, making understanding these shapes relevant for students. Identifying and collecting examples from their environment helps them see the utility of what they are learning. This hands-on approach helps cement their understanding of different solid shapes and their characteristics.

Examples & Analogies

Consider how cereal boxes are cuboidal. Their shape allows for stacking and storage, making them easy to fit in kitchen cabinets. On the other hand, a bottle of shampoo is cylindrical—its shape is perfect for pouring. These examples help to bridge the gap between theoretical learning and real-world applications.

Properties of a Cylinder

Unlock Audio Book

Signup and Enroll to the course for listening the Audio Book

Did you notice the following: The cylinder has congruent circular faces that are parallel to each other (Fig 9.12). Observe that the line segment joining the center of circular faces is perpendicular to the base. Such cylinders are known as right circular cylinders.

Detailed Explanation

Cylinders, specifically right circular cylinders, are defined by having two identical circular faces with a curved surface connecting them. Understanding that the centers of these circles are aligned vertically emphasizes the solid’s stability. This property is particularly important in their applications, such as in containers, pipes, and columns. The parallel nature of the faces leads to discussions about symmetry and stability in objects.

Examples & Analogies

Imagine a can of soda. Its shape allows for easy stacking on supermarket shelves and keeps the contents stable and secure inside due to its circular ends and smooth curved surface. This shape is designed for both efficiency and user convenience.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Cuboid: Defined by six rectangular faces, opposite faces are congruent.

  • Cube: A special cuboid with all square faces.

  • Cylinder: Defined by a curved surface and two congruent circular bases.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • A shoebox is an example of a cuboid.

  • A dice is an example of a cube.

  • A soup can represents a cylindrical shape.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎵 Rhymes Time

  • Cuboid is flat and has some pairs, Cube is all square and it compares, Cylinder rolls smooth, has no sharp stares.

📖 Fascinating Stories

  • Once upon a time, in a land of shapes, Cuboid, Cube, and Cylinder lived without scrapes. They all had their shapes, some thick and some thin, each doing their work with a mathematical grin.

🧠 Other Memory Gems

  • Remember 'CCP' for Cylinders: Curved surface, Congruent circles, and Perpendicular height.

🎯 Super Acronyms

CUBES stands for

  • Congruent Faces
  • Uniform Dimensions
  • Box Shape
  • Essential for calculations
  • Solid.

Flash Cards

Review key concepts with flashcards.

Glossary of Terms

Review the Definitions for terms.

  • Term: Cuboid

    Definition:

    A three-dimensional shape with six rectangular faces.

  • Term: Cube

    Definition:

    A special case of a cuboid where all six faces are squares and are congruent.

  • Term: Cylinder

    Definition:

    A three-dimensional shape with one curved surface and two circular faces.

  • Term: Congruent Faces

    Definition:

    Faces that are identical in shape and size.