Fundamental Concepts (Geometry)
ICSE Class 6 · Mathematics · Chapter 23
What this chapter covers
- Geometry in everyday life
- Point, line, line segment and ray
- Plane and intersecting lines
- Open and closed figures
- Measuring a line segment
Key points
- Geometry is the study of points, lines, shapes and sizes, and you meet it everywhere in daily life.
- A point shows an exact position and has no size.
- A line goes on without end in both directions and cannot be measured.
- A line segment has two end points and a fixed length that can be measured.
- A ray has one end point and goes on without end in one direction.
- Exactly one straight line passes through two different points; many lines pass through one point.
- A plane is a flat surface that goes on without end in all directions.
- Intersecting lines meet at one common point, called the point of intersection.
- An open figure has ends that do not meet; a closed figure has no gap in its boundary.
- A closed figure has an interior, a boundary and an exterior.
- A linear figure has a boundary of line segments; a curvilinear figure has a boundary of curves.
- A line segment is measured with a ruler, or more exactly with a divider and a ruler, starting from the 0 mark.
Questions answered
How many end points does a line have? How many does a ray have?
A line has no end points. A ray has one end point, called its initial point.
Which of these can be measured: a line, a line segment or a ray?
Only a line segment can be measured, because it has two end points.
Give one everyday object that is a model of a ray.
A beam of light from a torch.
How many straight lines can pass through two different points?
Exactly one.
At how many points can two different straight lines intersect?
At only one point.
Is the letter M an open or a closed figure? Is the letter O open or closed?
M is an open figure. O is a closed figure.
A goat is tied inside a round fence. Is the goat in the interior or the exterior of the fence?
In the interior.
Is a triangle a linear or a curvilinear figure?
A triangle is a linear figure, because its boundary is made only of line segments.