NCERT Exemplar Solutions
Class 6 - Mathematics - Unit 9: Symmetry and Practical Geometry - Multiple Choice Questions
Question 8

Question.  8

The instrument to measure an angle is a

(A)

Ruler

(B)

Protractor

(C)

Divider

(D)

Compasses

Detailed Answer with Explanation:

Why the correct answer is Protractor

Simple idea: To measure how wide an angle opens, we use a tool that has degree markings (0° to 180° or 0° to 360°). That tool is a protractor.

What each tool does

  • Ruler: Measures length in cm/mm. It does not measure angles.
  • Protractor: Measures angles in degrees (°). ✔️
  • Divider: Has two sharp legs; used to mark equal lengths or transfer distances.
  • Compasses: Used to draw circles or arcs.

How to use a protractor (very easy steps)

  1. Find the vertex of the angle.

    Example angle: ( angle ABC )

    The vertex is the middle letter: ( B )

  2. Place the protractor so that its small center hole (or cross) is exactly on the vertex.

    Center of protractor → ( B )

  3. Align the baseline of the protractor with one arm of the angle.

    Baseline (0° line) should lie on one arm through ( B )

  4. Choose the correct scale on the protractor.

    If the angle opens to the right, start reading from the 0° on the inner scale.

    If it opens to the left, start from the 0° on the outer scale.

  5. Read the number where the other arm of the angle cuts the scale.

    Suppose it meets at ( 60^circ )

    So, ( angle ABC = 60^circ )

Quick checks (to avoid mistakes)

  • Is the center of the protractor exactly at the vertex? → ( B )
  • Is one arm aligned with the 0° line?
  • Did you pick the correct scale (inner or outer) that starts from 0° on your aligned arm?

Conclusion

The instrument that measures an angle is a Protractor.

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