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This pdf covers, classifying angles on the basis of degree measurements for the proper understanding. Sample questions along with answers have also been provided.

1.
Class Notes

Class - V Topic - Chapter – 2

Subject - Mathematics Shapes And Angles

Classification of Angles

On the basis of degree measurements the angles are classified.

Acute angle – An angle whose measure is more than 00 and less

than 900 is called an acute angle.

Example - ∠CBA is an acute angle.

∠CBA = 600

Right angle – An angle whose measure is 900 is called a right angle.

Example – ∠AOB is a right angle.

∠AOB = 900

Obtuse angle – An angle whose measure is more than 900 and less

than 1800 is called an obtuse angle.

Example - ∠DOQ is an obtuse angle.

∠DOQ = 1200

Class - V Topic - Chapter – 2

Subject - Mathematics Shapes And Angles

Classification of Angles

On the basis of degree measurements the angles are classified.

Acute angle – An angle whose measure is more than 00 and less

than 900 is called an acute angle.

Example - ∠CBA is an acute angle.

∠CBA = 600

Right angle – An angle whose measure is 900 is called a right angle.

Example – ∠AOB is a right angle.

∠AOB = 900

Obtuse angle – An angle whose measure is more than 900 and less

than 1800 is called an obtuse angle.

Example - ∠DOQ is an obtuse angle.

∠DOQ = 1200

2.
Straight Angle – An angle whose measure is equal to 1800 is called

a straight angle.

Example - ∠XOY is a straight angle.

∠XOY = 1800

Reflex Angle – An angle whose measure is more than 1800 and less

than 3600 is called a reflex angle.

Example - ∠RST is a reflex angle.

∠RST = 2200

Complete Angle – An angle whose measure is equal to 3600 is

called a complete angle.

Example - One complete rotation around P R S

a point P makes 3600 angle.

Here ∠SPR = 3600

Combination of Angles

Complementary Angles – Two angles are complementary if their

sum is equal to 900.

Example - ∠ABC = 600 , ∠CBD = 300 A

Here ∠ABC + ∠CBD = 600 + 300 = 900 C

So ∠ABC and ∠CBD are Complementary

Angles. B D

a straight angle.

Example - ∠XOY is a straight angle.

∠XOY = 1800

Reflex Angle – An angle whose measure is more than 1800 and less

than 3600 is called a reflex angle.

Example - ∠RST is a reflex angle.

∠RST = 2200

Complete Angle – An angle whose measure is equal to 3600 is

called a complete angle.

Example - One complete rotation around P R S

a point P makes 3600 angle.

Here ∠SPR = 3600

Combination of Angles

Complementary Angles – Two angles are complementary if their

sum is equal to 900.

Example - ∠ABC = 600 , ∠CBD = 300 A

Here ∠ABC + ∠CBD = 600 + 300 = 900 C

So ∠ABC and ∠CBD are Complementary

Angles. B D

3.
Supplementary Angles – Two angles are supplementary if their

sum is equal to 1800.

Example - ∠BOA = 1200, ∠AOC = 600

Here ∠BOA + ∠AOC = 1200 + 600 = 1800

So ∠BOA and ∠AOC are Supplementary

Angles in Clock

There are 12 equal divisions in a clock

for each hour. We know that one

complete rotation makes 3600 angle.

So angle formed between any two

consecutive numbers in a clock is

360

= 12

= 300

• We can estimate the measure of angle formed by counting

the number of divisions between the hour hand and minute

hand multiply with 300.

• We take the shortest path to do it.

• We can also tell the type of angles formed.

Example - At 8 ‘o’ clock the there are 4 gaps of 300

So the angle formed = 4 x 300 = 1200

sum is equal to 1800.

Example - ∠BOA = 1200, ∠AOC = 600

Here ∠BOA + ∠AOC = 1200 + 600 = 1800

So ∠BOA and ∠AOC are Supplementary

Angles in Clock

There are 12 equal divisions in a clock

for each hour. We know that one

complete rotation makes 3600 angle.

So angle formed between any two

consecutive numbers in a clock is

360

= 12

= 300

• We can estimate the measure of angle formed by counting

the number of divisions between the hour hand and minute

hand multiply with 300.

• We take the shortest path to do it.

• We can also tell the type of angles formed.

Example - At 8 ‘o’ clock the there are 4 gaps of 300

So the angle formed = 4 x 300 = 1200

4.
Questions For Practice

Q1. Write any 3 examples of 2D and 3D shapes.

Ans . 2 Dimensional Shapes – Square, Rectangle, Triangle

3 Dimensional Shapes – Cone, Sphere, Cube

Q2. Write the types of angles for the given measurement.

(a) 790 (b) 1900 (c) 2890 (d) 1430 (e) 3600 (f) 1800

Ans . (a) 790 - Acute angle (b) 1900 - Reflex Angle

(c) 2890 - Reflex Angle (d) 1430 - Obtuse Angle

(e) 3600 - Complete Angle (f) 1800 - Straight Angle

Q3. In the given figure write the names of

(a) all the angles formed.

(b) all the arms of the angles formed.

(c) vertex of the angles.

Ans. (a) All angles:- ∠DOC, ∠DOB, ∠DOA, ∠COB, ∠COA, ∠BOA

(b) All arms :- DO, CO, BO, OA (C) Vertex :- O

Q4. Look at the pictures given below and write the types of the

angle. (a) (b) (c)

Ans. (a) Acute Angle (b) Obtuse Angle (c) Right Angle

Q1. Write any 3 examples of 2D and 3D shapes.

Ans . 2 Dimensional Shapes – Square, Rectangle, Triangle

3 Dimensional Shapes – Cone, Sphere, Cube

Q2. Write the types of angles for the given measurement.

(a) 790 (b) 1900 (c) 2890 (d) 1430 (e) 3600 (f) 1800

Ans . (a) 790 - Acute angle (b) 1900 - Reflex Angle

(c) 2890 - Reflex Angle (d) 1430 - Obtuse Angle

(e) 3600 - Complete Angle (f) 1800 - Straight Angle

Q3. In the given figure write the names of

(a) all the angles formed.

(b) all the arms of the angles formed.

(c) vertex of the angles.

Ans. (a) All angles:- ∠DOC, ∠DOB, ∠DOA, ∠COB, ∠COA, ∠BOA

(b) All arms :- DO, CO, BO, OA (C) Vertex :- O

Q4. Look at the pictures given below and write the types of the

angle. (a) (b) (c)

Ans. (a) Acute Angle (b) Obtuse Angle (c) Right Angle

5.
Q5. Look at the angles formed in the pictures given below and fill

the table with tickmark for the angles.

Q6. Look at the times in the clocks. Write the time and type of

angles formed.

the table with tickmark for the angles.

Q6. Look at the times in the clocks. Write the time and type of

angles formed.

6.
Q7. Fill in the blanks.

(a) At _____and _____ times in the clock right angle forms.

Ans. 9 ‘o’ clock, 3 ‘o’ clock

(b) At ________time straight angle forms in the clock.

Ans. 6 ‘o’ clock

(c) Two right angles make a _____angle. Ans. Straight

(d) Quarter of a complete angle is _____angle. Ans. Right

1

(e) 6 of a straight angle = ______degree. Ans. 30

Q8. Count the the number of right angles and number of angles

more than right angles in the these names.

(a) REENA (b) MEERA

Name Number of Number of angles more

right angles. than right angles.

(a) REENA 8 2

(b) MEERA 8 3

The above content has been prepared absolutely from home.

(a) At _____and _____ times in the clock right angle forms.

Ans. 9 ‘o’ clock, 3 ‘o’ clock

(b) At ________time straight angle forms in the clock.

Ans. 6 ‘o’ clock

(c) Two right angles make a _____angle. Ans. Straight

(d) Quarter of a complete angle is _____angle. Ans. Right

1

(e) 6 of a straight angle = ______degree. Ans. 30

Q8. Count the the number of right angles and number of angles

more than right angles in the these names.

(a) REENA (b) MEERA

Name Number of Number of angles more

right angles. than right angles.

(a) REENA 8 2

(b) MEERA 8 3

The above content has been prepared absolutely from home.