Subject Mathematics

Grade 5th

Students` Learning Outcomes

  • Use protractor to construct, right angle, straight angler and reflex angles of different measures

Information for Teachers

  • A protractor is a tool, typically made of transparent plastic, for measuring angles. Protractor is used to measure angles in degrees (0) in geometry lessons in schools. 


  • The circle outside an angle`s arms is termed as Exterior Angle.
  • The exterior angle of an obtuse angle or acute angle is known as Reflex Angle.
  • A Reflex Angle is one which is more than 1800 but less than 3600


  • Consult text book at all steps where and when required.

Material / Resources

Writing board, chalk / marker, duster, geometry box, textbook


  • Ask students if they have seen sun rise or sun set?


  • Draw a straight line on board and make half sun and ask how it looks at this time [show sample to the students].  
  • Tell them to open their geometry box and see if there is something resembling that.



  • Let them explore that the shape of protractor resembles a half sun.
  • Ask them to DRAW SUNRISE by using protractor, the way you drew on the board. [Show sample]
  • Let them try, later helping them to draw on the board with the help of a protractor.
  • Ask them to read and find total number of degrees on this D- shaped tool.
  • May be they will answer 1800 or something else.
  • Tell them that this is also an angle called straight angle.
  • Tell the students that there are 1800 degrees in a straight angle. Ask students if they have ever heard the phrase “does a one-eighty”. It means to do things in opposite direction.
  • Let them try to join two protractors in a way to complete a whole circle and then ask then count number of degrees it has.
  • Let them explore that there are 3600 degree in a circle.



Activity 1

  • Recall the concepts of angles which they have already studied in Grade 4
  • Conduct one or two activities from previous grade if you find necessary.
  • This will help to create a link.
  • Make angle 4 of 1800by the hands of the clock; make the figure then change 4 directions.
  • Encourage students to get ready for the game: Do as I do?
  • Attempt following steps on board and ask students to do the same individually.


  • Place the center of protractor at a point A which is point O.
  • Look for the number 1800on protractor and mark a point on the paper next to 1800
  • Take away the protractor and label the point C.
  • Join point A and new point C by using ruler.



  • Relate the clock hands and angles that 12 0` Clock is a Zero degree angle and 6 0` Clock is 1800angle. [Change the direction of Minute and Hour hand to form new angle]


Sum up / Conclusion

  • Ask students what they have learnt during the period about the angles.
  • Student will answer that angle of 1800 is called straight angle.


  • Reflex Angle is one which is more than 1800 but less than 3600



  • Reflex angle is larger angle, whereas its smaller angle may be acute or obtuse.



  • Give angles of different degrees to the students and ask them to draw them and identify its type.

i.                    450

ii.                   1700

iii.                  900

iv.                  200

v.                   1800

vi.                  3600

Follow up

  • Ask students to look for examples that show straight and reflex angles in their surroundings.


  • Added 1800 in the noted angle that would be the required reflex angle, For example 450+ 1800 = 2250
  • Reflex angle will be 1800




Leave a Comment