##### Question 1:

Complete the following table:

##### Answer:

Complete table is as follow:

##### Question 2:

Here you find four nets (Figure). There are two correct nets among them to make a tetrahedron. See if you can work out which nets will make a tetrahedron.

##### Answer:

In given figures part (i) and part (iii) are two correct nets for a tetrahedron.

##### Question 3:

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

##### Answer:

Nets in (ii), (iii), (iv) and (vi) form cubes.

##### Question 4:

##### Answer:

##### Question 5:

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

##### Answer:

Reason: Because one pair of opposite faces will have 1 and 4 on them whose total is not 7 and another pair of opposite faces will have 3 and 6 on them whose total is also not 7.

##### Question 6:

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).

##### Answer:

##### Question 7:

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

##### Answer:

Dimensions of cuboid are 5 cm, 3 cm and 2 cm. By changing length, breadth and height, we get three different isometric sketches of cuboid are as follow:

##### Question 8:

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.

##### Answer:

##### Question 9:

Try to guess the number of cubes in the following arrangements (Fig.) :

##### Answer:

Number of cubes in the arrangements are as
follows:

(i) 24 cubes (ii) 8 cubes

(iii) 9 cubes.

##### Question 10:

##### Answer:

Numbers on the opposite face:

(a) 5 + 6 is 2 + 1

and (b) 4 + 3 is 3 + 4.

##### Question 11:

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 die

(d) A circular pipe

(e) An ice cream cone.

##### Answer:

When we give a vertical cut then following
cross-sections are obtained:

(a) A brick — Cuboid

(b) A round apple — Circular

(c) A die — Square

(d) A circular pipe — Circular

(e) An ice cream cone — Curved shape

When we give a horizontal cut then following
cross-sections are obtained:

(a) A brick —Cuboid

(b) A round apple —Circular

(c) A die —Cuboid

(d) A circular pipe —Hemispherical

(e) An ice cream cone —Frustrum

##### Question 12:

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.)

##### Answer:

##### Question 13:

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 !)

##### Answer:

Shadows of some 3-D objects, when seen under the lamp of an overhead projector.

##### Question 14:

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

- TRUE
- FALSE

##### Answer:

TRUE

##### Question 15:

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

- TRUE
- FALSE

##### Answer:

FALSE

##### Question 16:

For each solid, the three views (1), (2), (3) are given. Identify for each solid the corresponding top, front and side views.

##### Answer:

(1) Front (2) Side (3) Top

##### Question 17:

For each solid, the three views (1), (2), (3) are given. Identify for each solid the corresponding top, front and side views.

##### Answer:

(1) Top (2) Side (3) Front

##### Question 18:

For each solid, the three views (1), (2), (3) are given. Identify for each solid the corresponding top, front and side views.

##### Answer:

(1) Side (2) Front (3) Top

##### Question 19:

##### Answer:

(1) Side (2) Top (3) Front