Ex-19.1 & 19.2, Visualising Solid Shapes, Class 7, Math RD Sharma Solutions | RD Sharma Solutions for Class 7 Mathematics PDF Download

Exercise 19.1

Question 1:

Complete the following table and verify Euler's formula in each case.
 

Faces (F)	6	4	9	7
Edges (E)	12	6	16	15
Vertex (V)	8	4	9	10

Answer 1:

Hence Euler's formula is verified for these figures.

Question 2:

Give three examples from our daily life which are in the form of (i) a cone (ii) a sphere (iii) a cuboid (iv) a cylinder (v) a pyramid.

Answer 2:

Examples of

(i) Cone: Ice-cream cone, clown cap, rocket
(ii) Sphere: Football, a round apple, an orange
(iii) Cuboid: book, brick, duster
(iv) Cylinder: circular pipe, glass, circular pole
(v) Christmas decorations, cheese and patio umbrellas. 

Exercise 19.2

Question 1:

Match the following nets with appropriate solids:

Answer 1:

Here
(a) → (ii)
(b) → (iii)
(c) → (iv)
(d) → (i)

Question 2:

Identify the nets which can be used to make cubes (cut-out the nets and try it):

Answer 2:

Only (ii), (iv) and (vi) form a cube.

Question 3:

Can the following be a net for a die? Explain your answer.

Answer 3:

Since, in a die, the sum of the number of opposite faces of a die is 7. In the given figure, it is not possible to get the sum as 7. Hence the given net is not suitable for a die.

Question 4:

Out of the following four nets there are two correct nets to make a tetrahedron. Identify them.

Answer 4:

For making a tetrahedron, only (i) and (iii) are suitable nets.

Question 5:

Here is an incomplete net for making a cube. Complete it in atleast two different ways.

Answer 5:

The complete nets for making a cube are Images