Measuring Angles Using a Protractor

We will read the measurement from the __________ scale.

• inner

• outer

Is this the correct way of using a protractor to measure angles?

• Yes

• No

∠DEF = ______°

• 34°

• °146

Is this the correct way of using a protractor to measure an angle

• Yes

• No

Do you think this is a 85° angle?

• Yes

• No

Why is this not a 85° angle?

• 85° is an acute angle. The picture shows a right angle as it is 90°.

• 85° is an obtuse angle. The picture shows an acute angle as it is less than 90°.

• 85° is an obtuse angle.The picture shows an acute angle as it is less than 90°.

• 85° is an acute angle. This picture shows an obtuse angle as it is more than 90°.

This is the wrong way of using a protractor because __________.

• the bottom line of the angle is not aligned to the baseline of the protractor.

• the vertex of the angle is not aligned to the centre of the protractor.

Do you agree that ∠a = 90°.

• Yes. The top line of the angle is aligned to 90°.

• No. The measurement is not accurate because the bottom line of the angle is not aligned to the baseline of the protractor.

We should read the measurement based on the inner scale because '0' starts from the ______.

• inner scale

• outer scale

∠a = ______°

• 75

• 85

• 105

• 115