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\ 08-Oct-2025 Bharat Arora Proof-9 Reader’s Sign _______________________ Date __________

Math Insight
Clockwise means moving in the direction of the hands of a clock.
Anticlockwise is a direction opposite to that of the normal
rotation of the hands of a clock.
Clockwise Anticlockwise

activity Experiential Learning

Š Take a circular paper cutout or a paper plate and mark a point
O at its centre.
Š Fold the circular cutout (or plate) exactly in half along the point

O and crease it firmly. O
Š Open it up. The crease is a straight line representing a straight
angle (180°) along point O.

Š Take another circular cutout (or plate) and fold it in half.
Š Now, fold that half again in half, lining up the straight edges of
the crease. O

Š Unfold it, the two creases will form a cross at point O. Each of
the four angles at the centre O represents a right angle (90°).

Š Now, fold another cutout into a quarter-circle (a 90° angle).
Š Fold this shape in half one more time.
Š Unfold the paper completely. The new creases have divided the O
circle into eight equal parts. Each small angle at point O is 45°,

which is an acute angle.

measuring an angle using a protractor

Let us measure the given ∠AOB using a protractor. To measure an angle B
using a protractor, follow the steps given below.
Step 1: Place the centre point of the protractor on the vertex O of the angle. A

Step 2: Adjust the protractor in such a way that the baseline coincides O
with the arm OA of the angle.

Outer
Scale 70 80 90 100 110
90
60 120 110 100 80 70 120 B
50 60 130
40 140 130 50 40 140 Inner
30 150 30 150 Scale
20 160 20 160
10 170 10 170
0 180 O 0 180 A
Step 3: Check the scale where the baseline arm points to 0°.

Step 4: Read the measure of the angle where the other arm crosses the scale.

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