Maharashtra Board Class 4 Maths Part One Chapter 1 Geometrical Figures PDF Download

Geometrical Figures

Angles

We see angles between the ground and the slide.

The ladder makes an angle with the ground.

We see angles between the tree trunk and its branches.

There is an angle between the electric pole and the ground.

In our surroundings, wherever we see two lines meeting, there is an angle.

Collect some pictures in which you can see angles. Mark those angles using a pencil.

Look at the angles that can be made at your elbow.

Teacher's Note

You see angles everywhere in your home. A door opening makes an angle. A window corner makes a right angle. Show your child these things.

Exam Trick

Remember: Angle = two lines meeting. When you open a door, it makes an angle with the wall. Practice finding angles around you.

Points to Remember

An angle is made when two lines meet at one point.

We can find angles in many places around us.

Your elbow can make different angles when you move your arm.

Right Angle, Acute Angle, Obtuse Angle

We see a right angle between two adjoining sides of a window.

Two adjacent sides of a book make a right angle.

In a clock, at 3 o'clock and 9 o'clock, the minute hand and the hour hand are at right angles to each other.

In the picture alongside, there is a right angle between the two blades of the scissors.

As we reduce the distance between the tips of the blades, little by little, the angle between the blades grows smaller than a right angle.

An angle which is smaller than a right angle is called an acute angle.

But, as we increase the distance between the tips of the blades the angle between the blades grows bigger than a right angle.

An angle that is bigger than a right angle is called an obtuse angle.

A right angle

An acute angle

An obtuse angle

Teacher's Note

Show your child the corner of a book. That is a right angle. When a door is half open, it makes an acute angle. When a door is wide open, it makes an obtuse angle.

Exam Trick

Remember: Right angle = 90 degrees = door corner. Acute angle = smaller angle = pencil tip. Obtuse angle = bigger angle = wide open door.

Points to Remember

A right angle looks like the corner of a book or a square.

An acute angle is smaller than a right angle.

An obtuse angle is bigger than a right angle.

We can see these angles in scissors, doors, and at our elbow.

Observe the figures below and write 'right angle', 'acute angle' or 'obtuse angle' in the box below each figure.

Make right angles by joining the dots in the box below.

Make acute angles by joining the dots.

Make obtuse angles by joining the dots.

Make a right angle, acute angle and obtuse angle at your elbow. Show these angles to your friends and check theirs.

Check! Is this true?

The angle an electric pole makes with the ground is a right angle.

The slide makes one acute angle and one obtuse angle with the ground.

The ladder makes one acute angle and one obtuse angle with the wall.

The angle between the thorns of the babul tree is an obtuse angle.

Leaving the thumb, the angles between any two adjoining fingers is an acute angle.

Activity: Observe in which places in your surroundings you find angles. Make right angles, acute angles and obtuse angles by folding paper.

Teacher's Note

Take your child to the school playground. Show where angles are. The goal post, the corner of the basketball court - all have angles. Let them touch and feel these angles.

Exam Trick

Remember three angles: Right = 90 degrees = normal corner. Acute = less than 90 = sharp. Obtuse = more than 90 = wide. Draw them in your test.

Points to Remember

Right angle is exactly like the corner of your notebook.

Acute angle is a pointy angle, smaller than right angle.

Obtuse angle is a wide angle, bigger than right angle.

All three angles are found in everyday things around us.

You can make all three angles with your arms and elbow.

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