18 Questions
What is the line that joins any two points on a circle called?
Radius
In a circle, what is a chord that passes through the center called?
Diameter
Which type of angle does the vertical margin line form with the horizontal lines?
Right angle
What type of relationship exists between parallel lines?
They never meet
If a line touches a circle at exactly one point, what is it called?
Tangent
What do all radii of a circle have in common?
They are all of the same length
What do the children inside the circle represent in the game described?
The 'sea'
What do points P, Q, R, and T represent in the interior of the circle?
Endpoints of an arc
What is defined as the circumference of a circle?
The distance around the boundary of the circle
If a circle's circumference is 37.68 cm, what is its radius?
$9 , \text{cm}$
In a plastic bangle splitting at points A and B, what do the resulting parts represent?
Arcs of the circle
If points P and Q divide a circle into two arcs, what must be true about points P and Q?
They are located at any two positions on the circle
If the radius of a circle is 7 cm, what will be the length of its diameter?
14 cm
How does the length of a diameter compare to the length of a radius?
Twice the length
If another diameter CD is drawn on the same circle, what can be said about its length compared to diameter AB?
They are equal in length
In 'Land and Sea' played inside a circle on the playground, what geometric concept could be related to this game?
Perimeter
What is the relationship between the radius and diameter of a circle?
Radius is half the length of the diameter
If the radius of a circle is 10 cm, what will its perimeter be?
40π cm
Study Notes
Circle Basics
- In the game "Land and Sea", children inside the circle are in the "sea" and those outside are on "land".
- The colored area inside the circle is the interior of the circle.
- Points inside the circle are in the interior, points on the circle are on the circle, and points outside the circle are in the exterior.
Circumference of a Circle
- The circumference of a circle is the length of the circle around its edge.
- It can be measured by winding a string around the circle and then straightening it out.
- The circumference of the circle in the example is 12 cm 3 mm.
Arc of a Circle
- An arc of a circle is a part of the circle.
- If a circle breaks at two points, it will split into two arcs.
- The points where the circle breaks are the end points of both arcs.
Radius, Chord, and Diameter
- A radius of a circle is a line joining the center of the circle to any point on the circle.
- A circle has many radii, all of the same length.
- A chord is a line joining any two points on a circle.
- A chord passing through the center of the circle is called a diameter.
- A diameter is twice the length of its radius.
- All diameters of a circle are of the same length.
Interior and Exterior of a Circle
- The interior of a circle is the area inside the circle.
- The exterior of a circle is the area outside the circle.
- Points inside the circle are in the interior, points on the circle are on the circle, and points outside the circle are in the exterior.
Test your knowledge on parallel and perpendicular lines by giving examples from your environment and determining the relationship between lines in provided pictures.
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