Hinglish

Comparing Angles and Rotating Arms

Class 6 Maths · Chapter 2: Lines and Angles · NCERT Ganita Prakash section 2.6–2.7

Learn

Animals open their mouths a little or a lot: the more the jaws turn, the bigger the angle. To compare two angles we can trace one and put it on top of the other, with the vertices together. This is called superimposition.

If the vertices match and both arms lie on top of each other, the two angles are equal: the same amount of turn.

Careful! Longer arms do not make a bigger angle. Only the turn matters. Angle A has long arms, but angle B is bigger.

Without tracing, we can use a transparent circle: put its centre on the vertex, mark where the arms cross its edge, then place it on the other angle and see which opening is wider.

Rotating arms: two straws joined with a paper clip. Only arms with exactly the right angle pass through an angle-shaped slit. Make the angle that fits a 60° slit.

Remember

  • Compare angles by putting one on the other with the vertices together (superimposition).
  • Equal angles: the vertex and both arms lie on top of each other.
  • The length of the arms does not change the size of an angle.

Quick check

Angle A has arms 10 cm long and opens a little. Angle B has arms 3 cm long and opens much wider. Which angle is bigger?

  1. Angle A
  2. Angle B
  3. They are equal
Answer

Angle B. The size depends on the turn, not on the arm length. B opens wider, so B is bigger.

Think about it

Can you make an angle smaller by cutting its arms shorter?

One answer

No. Shorter arms still need the same turn to move onto each other, so the angle stays the same.

Practice

Practise with fresh questions at three levels (easy, medium, hard), some answered hands-on, with hints and worked answers. Get 4 of your last 5 right to finish the topic.