Problem Set 25 – Measuring Angles with a ProtractorClass 5 Maths · Chapter 6 Angles · Problem Set 25 – Maharashtra Board

Summary: Problem Set 25 – Measuring Angles with a Protractor

To measure an angle, put the centre of the protractor exactly on the vertex.

Lay the baseline of the protractor along one arm of the angle.

Start counting from the 0 on the side where that arm lies, and read the number where the other arm crosses the edge.

If an arm is too short to reach the numbers, make it longer with a ruler. A longer arm does not change the size of the angle.

You can lay the baseline on either arm — the measure comes out the same.

Key points to remember

• Centre of protractor on the vertex
• Baseline along one arm
• Count from the 0 on that arm's side
• Read where the second arm crosses the edge
• Extending the arms does not change the angle
• Same answer from either arm
• Acute angle → reading less than 90°
• Obtuse angle → reading more than 90°

Problem Set 25 – Measuring Angles with a Protractor – Notes

1. Step 1 – Place the protractor

• Find the small mark at the centre of the protractor's straight edge.
• Put this centre mark exactly on the vertex of the angle.
• Turn the protractor until its baseline lies right on top of one arm.

2. Step 2 – Choose the right 0

• The protractor has two rows of numbers. Do not just read any row!
• Look at the arm under the baseline. Is it on the right of the vertex or on the left?
• If the arm goes to the right, count 10, 20, 30… from the 0 on the right. If it goes to the left, count from the 0 on the left.

3. Step 3 – Read the measure

• Follow the scale you chose up to the place where the other arm crosses the curved edge.
• The number there is the measure of the angle in degrees.
• Each small line between two numbers is 1°. Count them for answers like 55° or 105°.

4. When the arms are too short

• Sometimes the arms of a drawn angle stop before they reach the numbers on the protractor.
• Take the protractor away and make both arms longer with a ruler and pencil.
• The angle stays the same size — only the lines get longer. Now measure again.

5. Check your answer

• Before reading, decide: is the angle acute (smaller than a book corner) or obtuse (bigger)?
• If it looks acute, your answer must be less than 90°. If it looks obtuse, it must be more than 90°.
• Reading the wrong scale gives the other number: the two numbers at one mark always add up to 180. So 40° on one scale is 140° on the other.

Formulas at a glance

Key terms

Problem Set 25 – Measuring Angles with a Protractor – Flashcards

Read the question, answer it in your head, then tap the card to check. 10 cards.

Problem Set 25 – Measuring Angles with a Protractor – MCQ Quiz

10 questions. Tap an option — you will see at once if it is right and why.

How to study Problem Set 25 – Measuring Angles with a Protractor

⏱ About 25 minutes

1. Learn (5 min)
   Learn the three steps: centre on vertex, baseline on an arm, count from the right 0.
2. Measure (15 min)
   Draw 5 angles of any size and measure each one twice — once from each arm.
3. Practise (5 min)
   Do the 4 'Try it yourself' sums, take the quiz and play 🎮 Play.