Class 7 Maths

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.

net of cube net of cube net of cube net of cube net of cube net of cube

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.

net of dice net of dice

Answer:

net of dice net of dice

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

net of dice

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?

net of dice

Answer:

net of dice net of 3 D shape

Question 5: Match the nets with appropriate solids.

Column IColumn II
(a)net of 3 D shape(1)net of 3 D shape
(b)net of 3 D shape(2)net of 3 D shape
(c)net of 3 D shape(3)net of 3 D shape
(d)net of 3 D shape(4)net of 3 D shape

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