By studying this lesson, you will be able to,
● identify items which have the circular shape and
● create circular designs using items which have the circular shape.
1.1 Identifying items which have the circular shape
A figure of a purple circular shaped card is given here.
Pictures of several more items, in which the circular shape can be observed are given below.
Exercise 1.1
(1) From the following items, select and write down the ones in which the circular shape can be observed.
(i) The mathematics text book
(ii) Drum
(iii) Cricket bat
(iv) Sieve
(v) Winnowing fan
(vi) Wheel of a vehicle
(vii) Steering wheel of a car
(viii) Tea spoon
(ix) Pot
1.2 Drawing circles using items
The following figures illustrate how the circular shape is drawn using various items that have the circular shape. Carefully observe the figures and then engage in the following activity.
The figure drawn in the above activity using the two rupees coin is shown here. The complete curved line of such a figure is known as a circle.
Observe that the circles drawn in the above manner are different from each other in size.
Through this activity, the fact that the distance from the point where the fold lines which divide the circular lamina into two equal parts intersect, to any point on the curved edge of the lamina is the same is established.
Compare the figure you obtained by doing the above activity, with the figure given here.
In this manner, you will be able to identify the positions inside the circle, on the circle and outside the circle.
Exercise 1.2
(1) From the collection of items given below, select the ones that can be used to draw circles and write down the corresponding numbers.
(2) From the figures shown below, select those which are circles and write down the corresponding numbers.
(3) Select various items which have the circular shape, and using them draw several circles which are different in size to each other
(4) In this figure,
(i) which letters indicate positions inside the circle?
(ii) which letters indicate positions on the circle?
(iii) which letters indicate positions outside the circle?
(5) In a competition of throwing darts onto a circular board by standing at a location in front of it, 10 points are awarded if the dart hits the circle and 5 points are awarded if the dart hits the inside of the circle. But, no points are awarded if the dart hits the outside of the circle.
A group of students participated in the above competition. The figure indicates where the darts thrown by each of the students hit the board.
(i) Who are the students who were awarded 10 points?
(ii) Who are the students who were awarded 5 points?
(iii) Who are the students who did not receive any points?
(iv) If each of these student is given two more opportunities to throw darts, what is the maximum number of points that Mohan could receive in total?
1.3 Creating circular designs
Three circular designs created using circles are shown below. Such designs can frequently be seen on clothing materials, festival decorations and in religious places.
Create various designs as in the above activity, by moving the coin along different curved lines as well and drawing circles.
One such design is shown here.
