3rd Class Mental Ability Shapes Geometrical Shapes

Geometrical Shapes

Category : 3rd Class

Geometrical Shapes

OBJECTIVE

•    To identify different objects which represent some kind of geometrical shapes which we are coming across in our day to day life (Both 2D and 3D).
•     To recognize different parts of various geometrical shapes such as vertex and sides of a particular geometrical pattern.
•      Use of different geometrical shapes for creating Tangrams.
•      Knowledge of line of symmetry (horizontal and vertical).

Geometric Shapes

A geometric shape is defined as a set of points or vertices and sides connecting to the point to form a closed entry. There are various kinds of geometrical shapes. Based upon the number of vertices and sides they are identified as-follows:

2D Geometric Shapes

 Triangle ·         Triangle has three sides. ·         It has three vertices. Square ·         Squares have 4 equal sides and 4 right angles. ·         They have 4 lines of symmetry. ·         All squares belong to the rectangle family. ·         All squares belong to the rhombus family. ·         All squares are also parallelograms. Rectangle ·         Rectangles have 4 sides and 4 right angles. ·         They all have 2 lines of symmetry (4 lines if they are also a square) ·         All rectangles belong to the parallelogram family. Rhombus ·         Rhombuses (rhombii) have 4 equal sides. ·         Both pairs of opposite sides are parallel. ·         They all have 2 lines of symmetry (4 lines if they are a square) ·         All rhombuses belong to the parallelogram family. Parallelogram ·         Parallelograms have 2 pairs of parallel sides. ·         Some parallelograms have lines of symmetry (depending on whether they are also squares, rectangles or rhombuses), but most do not. Circle ·         Circles have a point in the centre from which each point on the diameter is equidistant. ·         They have infinite lines of symmetry. Ellipse ·         Ellipses are like circles which have been squashed or stretched. ·         They have 2 lines of symmetry. ·         They are also a special type of oval. ·         The longest and shortest diameters of the ellipses are called the major and minor axis. These axis are also the lines of symmetry. Crescent ·         Crescent shapes are made when two circles overlap, or when one circle is removed from another circle. ·         The perimeter of crescents made from two circular arcs. ·         They have one line of symmetry. ·         Our moon forms crescent shapes during its phases. Pentagon ·         5 sided polygon Hexagon ·         6 sided polygon Heptagon ·         7 sided polygon Octagon ·         8 sided polygon

3D Geometric Shapes

 Cube ·         Cubes have 6 faces, 12 edges and 8 vertices. ·         All sides on a cube are equal length. ·         All faces are square in shape. ·         A cube is a type of cuboid. Cuboid ·         Cuboids have 6 faces, 12 edges and 8 vertices. ·         All the faces on a cuboid are rectangular. Sphere ·         Spheres have either 0 or 1 faces, 0 edges and 0 vertices. Cylinder ·         Cylinders have either 2 or 3 faces, 0 or 2 edges, and 0 vertices. Cone ·         Cones have either 1 or 2 faces, 0 or 1 edge, and 1 apex (which is described by some mathematicians as a vertex).

Regular Geometric shape

The geometric shapes whose all sides are equal sides and equal interior angles are known as regular geometric shape.

Irregular Geometric Shapes

The geometric shapes which have sides and angles of any length and size.

Example - 1

Find the number of straight lines in the given figure.

(a) 8                              (b) 9

(c) 10                            (d) 11

Ans. (a)

Straight lines: AB, AC, BC, BE, CD, ED, AE and AD

So, number of straight lines = 8.

Example - 2

Komal built a birdhouse at summer camp. What shape is the piece of wood that was cut out to make the door other birdhouse?

(a) Triangle                                (b) Diamond

(c) Circle                                    (d) Pentagon

Ans. (c)

Circle shape is the piece of wood that was cut out to make the door of her birdhouse.

Example - 3

The figure has ____ straight lines and ______ curves.

(a) 9, 10                                    (b) 14, 12

(c) 16, 8                                    (d) 15, 10

Ans. (c)

The figure has 16 straight lines and 8 curves.

Directions (Example 4 - 5): Look at the figure carefully and answer the questions based on it.

Example - 4

How many more circles are there in the given figure than triangles?

(a) 15                            (b) 16

(c) 17                            (d) 18

Example - 5

Number of sleeping lines in the figure is _______.

(a) 21                            (b) 16

(c) 18                            (d) 19

Ans. (Example 4 - 5)

Ans. 4. (c)

Explanation

Number of circles in joker's cap = 10

Number of circles in joker's hand =6+6 =12

Number of circles in joker's face = 3

Number of circles in - triangle APQR = 5

Total number of circles =30

Number of triangles in feet = 4

Number of triangles in hands = 2

Number of triangles in face = 1

Number of triangles in $\Delta PQR=6$

Total number of triangles = 13

There are $30-13=17$more circles than triangles.

5. Ans. (a)

Explanation

Sleeping lines in jokes cap = 2

Sleeping lines in face = 2

Sleeping lines in neck =1

Sleeping lines in hands =4

Sleeping lines in $\Delta PQR=6$

Sleeping lines in legs =6

Total number of sleeping lines =21

Other Topics

30 20

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