To estimate and calculate the type and amount of degrees in an angle.
- Online activities:
- Other resources:
- Set of angle cards for each group showing the following - 90°, 180°, 270°, 360°, quarter turn, straight line, three-quarter turn, full turn, obtuse, acute, reflex, right angle
- Interactive whiteboard
- Right-angle finder (a circle with a right angle cut out)
- Strips of cardboard
- Split pins
- Protractors (optional)
You will need Adobe Acrobat reader to access the PDF files. BBC Webwise has a complete guide to downloading and installing Adobe Acrobat reader.
- Give each group an envelope containing the angle cards (see Resources).
- Explain to the children that they have one minute to match the cards to the correct angles.
- Discuss the results.
- Explain that angles are a measure of turn.
- Ask the children to stand behind their chairs and to rehearse physically turning a certain amount of degrees (eg "turn 180 degrees anti-clockwise", "turn 90 degrees to the right").
- Recap on the terms obtuse, acute, reflex and right angle. Give the groups those cards and explain that they have 30 seconds to group the angles into these new categories.
- Can the children think of ways to help remember these angles? Obtuse is an angle that is bigger than a right angle; it's 'fat' - obtuse sounds like obese, which means fat. Acute is an angle smaller than a right angle; small things can be cute - a cute angle is smaller than a right angle. A right angle is an exact corner; it's just right.
- Ask the class if they can think of a good way to remember that a reflex angle is bigger than 180° or a straight line.
Demonstrate the online activity on the whiteboard. Show the children how to drag the angle and squirt items. Once they understand how to use the activity, they can take it in turns to work through the rest of the program in small groups or in pairs on the class computer.
Lower ability - Using the right-angle finder, ask the children to first estimate and then find examples of right angles in the classroom.
Middle ability - Ask the children to get into pairs and use two strips of cardboard and a split pin to make angle strips. To do this, measure two equal strips of card, about 2 to 3 cm wide, and fix them together at one end using a split pin. The strips can be moved to make different types of angle. Ask the children to test each other in pairs - one can show an angle while their partner says if it's obtuse, right, acute and so on. The children can then find these types of angles around the classroom.
Higher ability - Follow the same activity as the middle ability group but extend it by asking the children to guess the degrees in the angle and then to check using a protractor.
Using a larger version of the children's angle strips, test them on the different types of angles and estimates of angle measures.
Ask the children to look around their houses for different angles and then draw and label them and estimate their measure in degrees (eg they could draw the angle of the corner of the kitchen window, label it as a right angle and estimate its measure at 90°).