NCERT Class 5 Mathematics Maths Mela Chapter 03 Angles as Turns PDF Download

Chapter 3: Angles as Turns

Note for Teachers

Encourage the learners to play the "statue" game. Learners can be asked to rotate themselves around and stop as the teacher announces "statue". The learners can notice how much they have turned with respect to their original position.

Can you recognise the child in the picture who has made a full turn? Who has made a half turn? How do you know? Discuss in class.

Give examples of real-life situations where you observe turns.

Ashutosh and Sahana are making circles, each having one foot fixed and rotating at one spot on the ground.

Ashutosh made a complete circle by making a full turn. Sahana is making a half-moon shape with a half turn.

The minute hand makes a full turn when it comes back to the initial position.

Teacher's Note

When you turn, think about what position you start in and where you end up. A full turn brings you back to face the same direction. A half turn makes you face the opposite direction. A quarter turn is like opening a door halfway. Watch the minute hand on a clock or trace your own turns to see these differences clearly.

A giant wheel makes a full turn when it comes back to the starting position E.

Reema takes two half turns in the same direction. It is like a ______turn.

What happens if she takes 2 quarter turns in the same direction?

It is like a ______turn.

What happens if she takes 4 quarter turns in the same direction?

It is like a ____ turn.

Write some of the everyday objects that involve turns. For example, taps, __________, __________, __________, __________, and __________.

What is the maximum possible turn in each of these cases? Check and tick.

• Do any of the above objects make a half turn? Write their names below - ........................................................................
• Do any of the above objects make a full turn? Write their names below - .........................................................................

Pragya joined a green and yellow straw with paper clips. She holds the green straw steady and turns the yellow straw around. Observe different turns of the yellow straw.

I made a quarter (\( \frac{1}{4} \)) of a full turn, so it looks like a right angle.

I made less than a quarter turn, so it looks like an acute angle.

Now I made more than a quarter turn, but less than a half turn. That looks like an obtuse angle.

I made two quarter turns. I wonder what it is called?

Angles arise in situations that involve a turn.

It is a straight angle.

Let Us Do

(a) Making a paper fan. Take a rectangular paper, fold every 2 cm as shown in the picture. Paste ice cream sticks as shown below to create a paper fan.

Use your paper fan to show different acute angles and obtuse angles.

Let us look at the turns made by the paper fan, keeping one side fixed.

Make an acute turn with the straws or fan. Continue to make another acute turn. Can the two acute turns together make another acute turn?

(b) You might have built houses using the hard covers of notebooks or cardboard pieces.

Look at the angles marked in the house. What angles are you able to see in this house? Write your answers as right, acute or obtuse angle.

A: ______________ B: _____________

C: ______________ D: _____________

E: ______________ F: _____________

G: ______________ H: _____________

(c) Make a 5-sided shape with 2 right angles, 2 obtuse angles, and 1 acute angle in your notebook.

Angle Measuring Tool

Let us make our tool to measure turns.

(a) Cut out a circle from a tracing paper and fold it to make 8 equal parts. Attach a straw to the centre and mark the starting point as shown.

(b) Now, try this.

• Show a \( \frac{1}{8} \) turn of the straw.
• Show a \( \frac{2}{8} \) turn. Show a \( \frac{1}{4} \) turn. Show a \( \frac{3}{8} \) turn.
• What angle have you made with a \( \frac{2}{8} \) turn? A \( \frac{1}{8} \) turn is half of a quarter turn.
• What angle have you made with a \( \frac{4}{8} \) turn? Continue turning by \( \frac{5}{8} \), \( \frac{6}{8} \), \( \frac{7}{8} \), and \( \frac{8}{8} \). Check when you have completed a \( \frac{3}{4} \) turn and a full turn.
• Now, cut out \( \frac{1}{8} \) part and \( \frac{2}{8} \) parts of the circle and paste them on a thicker paper or board. Use these as angle measuring tools.

(d) Look at the angle formation between the legs of these gymnasts. Identify whether the angles are acute, obtuse, right or straight.

Key Points

• A full turn brings you back to where you started. A half turn means you face the opposite direction. A quarter turn is one fourth of a complete rotation.
• A right angle is made by a quarter turn. An acute angle is less than a quarter turn, and an obtuse angle is between a quarter turn and a half turn.
• A straight angle is made by two quarter turns in the same direction, which equals a half turn.
• You can use fractions to describe turns: \( \frac{1}{4} \) turn, \( \frac{1}{8} \) turn, and so on. Different fractions of a turn create different types of angles.
• Angles appear in many everyday objects like doors, scissors, and taps, where one part rotates while another stays fixed.

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