Solid Shapes

Shapes with three dimensions are called solid shapes.
The corners of a solid shape are called its vertices. The line segments are called edges and flat surfaces are called faces.
A skeleton outline of a solid that can be folded to make the solid is called a net of that solid. A particular solid can have many types of nets.
An oblique sketch of a solid does not show proportional lengths. An isometric sketch shows proportional measurements of a solid. It is drawn on an isometric dot paper.
Different sections of a solid can be viewed in many ways.
- It can be done by cutting or slicing the shape. This would show the cross-section of the solid.
- It can be done by observing 2-D shadow of a 3-D shape.
- It can be done by looking at the shape from different angles; like front view, side view and top view.

Exercise 15.1

Question 1: Identify the nets which can be used to make cubes.

Answer: (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. Insert suitable numbers in the blanks, remembering that the number on the opposite face should total to 7.

Answer:

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

Answer: No, because 4 is opposite 1 and 3 is opposite 6 and they do not add up 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 in the net here?

Answer:

Question 5: Match the nets with appropriate solids.

Column I	Column II
(a)	(1)
(b)	(2)
(c)	(3)
(d)	(4)

Answer: (a) → 2, (b) → 3, (c) → 4, (d) → 1