NCERT Solutions for Class 7 Maths Chapter 13 Visualising Solid Shapes

 

NCERT Solutions for Class 7 Maths Chapter 13 Visualising Solid Shapes


Exercise 13.1 

1. Identify the nets which can be used to make cubes (cut out copies of the nets and try it):

(i)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 1

Solution:-

The given net cannot be folded as a cube.

Because, it can be folded as below,
NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 2

(ii)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 3

Solution:-

The given net can be folded as a cube.

Because, it can be folded as below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 4

(iii)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 5

Solution:-

The given net can be folded as a cube.

Because, it can be folded as below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 6

(iv)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 7

Solution:-

The given net can be folded as a cube.

Because, it can be folded as below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 8

(v)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 9

Solution:-

The given net cannot be folded as a cube.

Because, it can be folded as below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 10

(vi)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 11

Solution:-

The given net can be folded as a cube.

Because, it can be folded as below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 12

2. Dice are cubes with dots on each face. Opposite faces of a die always have a total of seven dots on them.

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 13

Here are two nets to make dice (cubes); the numbers inserted in each square indicate the number of dots in that box.

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 14

Insert suitable numbers in the blanks, remembering that the number on the opposite faces should total to 7.

Solution:-

(i)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 15

By observing the above figure the sum of the opposite faces is equal to 7.

So, the given net can be folded into a net of dice.

(ii)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 16

By observing the above figure the sum of the opposite faces is equal to 7.

So, the given net can be folded into a net of dice.

3. Can this be a net for a die?

Explain your answer.

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 17

Solution:-

The given net is folded as dice is shown in figure below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 18

No, this cannot be a net for a die.

By observing the figure we can say that, one pair of opposite face will have 1 and 4, another pair of opposite face will have 3 and 6 the sum of these two opposite faces are not equal to 7.

4. Here is an incomplete net for making a cube. Complete it in at least two different ways. Remember that a cube has six faces. How many are there in the net here?

(Give two separate diagrams. If you like, you may use a squared sheet for easy manipulation.)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 19

Solution:-

In the given net there are 3 faces and it can be completed as shown below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 20

5. Match the nets with appropriate solids:

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 21

Solution:-

(a) (ii)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 22
NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 23

Because, the net (ii) can be folded as a square.

(b) (iii)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 24
NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 25

Because, the net (iii) can be folded as a cylinder.

(c) (iv)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 26
NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 27

Because, the net (iv) can be folded as a cone.

(d) (i)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 28
NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 29

Because, the net (i) can be folded as a pyramid.


Exercise 13.2 

1. Use isometric dot paper and make an isometric sketch for each one of the given shapes:

(i)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 30

Solution:-

 

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 31

(ii)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 32

Solution:-

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 33

(iii)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 34

Solution:-

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 35

(iv)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 36

Solution:-

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 37

2. The dimensions of a cuboid are 5 cm, 3 cm and 2 cm. Draw three different isometric sketches of this cuboid.

Solution:-

From the question it is given that dimension of a cuboid are 5 cm, 3 cm, and 2 cm.

The three different isometric sketches of this cuboid is shown below,

1

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 38

2

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 39

3

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 40

3. Three cubes each with 2 cm edge are placed side by side to form a cuboid. Sketch an oblique or isometric sketch of this cuboid.

Solution:-

Oblique sketch

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 41

Isometric sketch

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 42

4. Make an oblique sketch for each one of the given isometric shapes:

(i)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 43

Solution:-

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 44

(ii)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 45

Solution:-

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 46

5. Give (i) an oblique sketch and (ii) an isometric sketch for each of the following:

(a) A cuboid of dimensions 5 cm, 3 cm and 2 cm. (Is your sketch unique?)

(b) A cube with an edge 4 cm long.

Solution:-

(a)

(i) Oblique sketch

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 47

(ii) Isometric sketch

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 48

(b)

(i) Oblique sketch

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 49

(ii) Isometric sketch

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 50


Exercise 13.3

1. What cross-sections do you get when you give a

(i) vertical cut (ii) horizontal cut

to the following solids?

(a) A brick

Solution:-

The cross-section of a brick when it is cut into vertically is as shown in the figure below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 51

The cross-section of a brick when it is cut into horizontally is as shown in the figure below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 52

(b) A round apple

Solution:-

The cross-section of a round apple when it is cut into vertically is as shown in the figure below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 53

The cross-section of a round apple when it is cut into horizontally is as shown in the figure below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 54

(c) A die

Solution:-

The cross-section of a die when it is cut into vertically is as shown in the figure below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 55

The cross-section of a die when it is cut into horizontally is as shown in the figure below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 56

(d) A circular pipe

Solution:-

The cross-section of a circular pipe when it is cut into vertically is as shown in the figure below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 57

The cross-section of a circular pipe when it is cut into horizontally is as shown in the figure below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 58

(e) An ice cream cone

Solution:-

The cross-section of an ice cream when it is cut into vertically is as shown in the figure below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 59

The cross-section of an ice cream when it is cut into horizontally is as shown in the figure below,

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 60


Exercise 13.4 

1. A bulb is kept burning just right above the following solids. Name the shape of the shadows obtained in each case. Attempt to give a rough sketch of the shadow. (You may try to experiment first and then answer these questions).

(i)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 61

Solution:-

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 62

The shape of the shadow obtained from a ball is a circle.

(ii)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 63

Solution:-

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 64

The shape of the shadow obtained from a cylindrical pipe is a rectangle.

(iii)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 65

Solution:-

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 66

The shape of the shadow obtained from a book is a rectangle.

2. Here are the shadows of some 3-D objects, when seen under the lamp of an overhead projector. Identify the solid(s) that match each shadow. (There may be multiple answers for these!)

(i)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 67

Solution:-

Cricket ball, water bottle cap, Disc

(ii)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 68

Solution:-

Die, chalk box etc.

(iii)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 69

Solution:-

Birthday cap etc.

(iv)

NCERT Solutions for Class 7 Maths Chapter 15 Visualising Solid Shapes Image 70

Solution:-

Book, keyboard, mobile, etc.

3. Examine if the following are true statements:

(i) The cube can cast a shadow in the shape of a rectangle.

Solution:-

The above statement is true.

(ii) The cube can cast a shadow in the shape of a hexagon.

Solution:-

The above statement is false.

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