Students often refer to Class 4 Maths Notes and Chapter 1 Shapes Around Us Class 4 Notes during last-minute revisions.
Class 4 Maths Chapter 1 Notes Shapes Around Us
Class 4 Maths Notes Chapter 1 – Class 4 Shapes Around Us Notes
→ Shapes define the outline or the boundary of an object, whether composed of lines, curves, or a combination of both. These can be two-dimensional (2D, flat) or three-dimensional (3D, solid). Each shape has a name based on its structure. A few examples of 2D shapes include circles, squares, rectangles, and triangles. In the same manner, the cube, cuboid, cone, cylinder and sphere are some basic 3D shapes.
→ When two rays or straight lines meet or intersect at a point, they form an angle. The rays or lines forming the angle are called the arms of the angle and the common point is called the vertex of the angle.
→ 2D shapes are flat figures with only length and width, while 3D shapes are solid objects with length, width, and height (or depth).
→ 2D shapes include: polygons (triangles, squares, rectangles, pentagons, hexagons, etc.), circles and ovals (these are curved 2D shapes).
→ A circle is a 2D round shape with all points on its edge (circumference) equally distant from its centre point.
→ The point in the middle of the circle, equidistant from all points on the circumference, is called the centre of the circle. The distance from the centre to any point on the circumference is called the radius of the circle.
→ A line segment that passes through the centre and has endpoints on the circumference is called diameter (which is twice the radius).
→ A prism is a 3D shape with two identical, parallel polygonal bases connected by rectangular or parallelogram-shaped faces.
→ Cube (square prism), cuboid (rectangular prism), triangular prism, etc., are some basic examples of prisms.
→ A pyramid has a single polygonal base and triangular faces that meet at a single point called the apex.
→ Triangular pyramids, Square pyramids, etc., are some basic examples of pyramids.
→ The net of a 3D shape is a 2D pattern used to describe what a 3D shape would look like if it were unfolded.
→ The surfaces of a solid that are flat or plane are called flat surfaces, and the curved surfaces are rounded surfaces that are not flat.
→ A sphere is a 3D round object. It does not have any edges or vertices. It has only one curved face.
→ When a horizontal and a vertical line meet at a point form a right angle.
→ An angle less than a right angle is called an acute angle.
→ An angle greater than a right angle is called an obtuse angle.
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