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NCERT Solutions for class 7 Maths chapter 15 – Visualizing Solid Shapes


Back Exercise

Exercise 15.1

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

Solution:
(ii), (iii), (iv) and (vi).

Question 2.
Dice are cubes with dots on each face. Opposite faces of a die always have a total of seven dots on them. Here are two nets to make dice (cubes); the numbers inserted in each square indicate the number of dots in that box.

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

Question 3.
Can this be a net for a die? Explain your answer.

Solution:
No, this cannot be a net for a die. Because one pair of opposite faces will have 1 and 4 on them and another pair of opposite faces will have 3 and 6 on them whose total is not equal to 7.

Question 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 on the net here? (Give two separate diagrams. If you like, you may use a squared sheet for easy manipulation).

Solution:
In the net given here three faces are shown.

Question 5.
Match the nets with appropriate solids:

Solution:
(a) ↔ (ii)
(b) ↔ (iii)
(c) ↔ (iv)
(d) ↔ (i)

Exercise 15.2

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


Solution:


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


Question 3.
Three cubes each with 2 cm edge are placed side by side to for,n a cuboid. Sketch an oblique or isometric sketch of this cuboid.
Solution:

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

Solution:

Question 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:



Exercise 15.3

Question 1.
What cross-sections do you get when you give a
(i) vertical cut
(ii) horizontal cut to the following solids?
(a) A brick
(b) A round apple
(c) A dice
(d) A circular pipe
(e) An ice cream cone.
Solution:

S.No. Vertical Cut Horizontal Cut
(a) (i) rectangle (ii) rectangle
(b) (i) circle (ii) circle
(c) (i) square (ii) square
(d) (i) circle (ii) rectangle
(e) (i) triangle (ii) circle

Exercise 15.4

Question 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):

Solution:

  1. a circle.
  2. a rectangle.
  3. a rectangle.

Question 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!)

Solution:

  1. → Sphere, cylinder
  2. → Cube, cuboid (of the square end)
  3. → Cone, the prism of the triangular base
  4. → Cylinder, the prism of the square base

Question 3.
Examine if the following are true statements:

  1. The cube can cast a shadow in the shape of a rectangle.
  2. The cube can cast a shadow in the shape of a hexagon.

Solution:

  1. True, the cube can cast a shadow in the shape of a rectangle.
  2. False, the cube can not cast a shadow in the shape of a hexagon.