Perimeter o The perimeter of a closed plane

Perimeter o The perimeter of a closed plane figure is the length of its boundary. 8 cm 10 cm 7 cm 8 cm 15 cm Perimeter = 15 + 8 + 10 + 8 + 7 = 48 cm

Perimeter o Square o Rectangle b=4 cm L= 8 cm P=8+5+8+5 P=l+b+l+b = 2(l + b) o Triangles b L=6 cm P=6+6+6+6 P=l+l+l+l = 4 l or 4 s c a P=a+b+c

Area o Area is the space within the boundary of a figure.

Area of a triangle h h b b o Area = ½ x base x height h b

A Circle is a plane figure made up of points that are equidistant ( at the same distance ) from the centre point. A circle has no corners and it is not made up of line segments. . .

CENTRE Centre is the fixed point of the circle. o O is the centre of the circle. All the points on the circle are equidistant from the centre.

A line segment which passes through the centre of a circle and whose end points lie on the circle is called diameter of the circle. A . 0 B AOB=DIAMETER

CIRCLE O = CENTRE P O S OS = RADIUS PQ = DIAMETER Q

Draw 3 circles of different sizes. Draw a radius and diameter for each of the circles. Find the lengths of the radius and the diameter. Length of diameter = 2 x length of radius Radius is half of diameter

Complete the table : RADIUS DIAMETER 2 cm 4 cm 6 cm 12 cm 5 cm 10 cm 2. 5 cm

A line segment whose endpoints are on the circle is called a chord of the circle. The line segment may or may not contain the centre of the circle. AB= CHORD A B Diameter is the longest chord.

Observe the figure and name the following : R P T O. 1. CENTRE : S 2. RADIUSOM, : OP, OS 3. DIAMETER: PS 4. CHORDS RT, PS : M O

Q 1. Draw a circle with centre O. 2. Mark four points P, Q, R, and S on it. R 3. Join OP, OQ, OR AND OS are all the radii of the circle. 4. Measure the length of OP, OQ, OR and OS. P OP, OQ, OR and OS are of equal length. We can draw a large number of radii of a circle and all the radii are of equal length. O S

DIAMETER DIVIDES THE CIRCLE IN TWO EQUAL PARTS. EACH PART IS SEMICIRCLE. SEMI CIRCLE IS HALF OF A CIRCLE. B A O C ABC IS AN ARC OF THE CIRCLE.

A PART OF THE CIRCLE IS CALLED AN ARC. A B AB = ARC

Distance around a circle is called circumference of a circle. We cannot find the length of a circle with the help of a scale. We can find its approximate length with the help of a thread. Circumference =3 x diameter

Group 1: Draw a circle and mark a point X on it. Draw as many chords as you can whose one endpoint is the point X. Also draw a chord which passes through the centre. Find the length of all the chords. Group 2: Draw a circle. Draw as many diameters of the circle as you can. Measure the lengths of the diameters drawn. How many diameters of a circle can we draw ? Are all the diameters of equal length? Group 3: The radius of a circle is 5 cm. What will be the length of its diameter?

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