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UNIT 17
Reasoning about
Shapes
For the next four days we are going to work on
shape and space, looking at the properties of 2D
and 3D shapes, increasing our understanding of
angles, and learning about rotation and
translation.
OBJECTIVES
• To identify, estimate and measure angles.
• To describe the properties of 2D and 3D shapes.
• To identify reflections, rotations and translations.
L ANGUAGE
obtuse, acute, right angle • scalene triangle, equilateral
triangle, right-angled triangle, isosceles
triangle • protractor • parallel, symmetry, line of symmetry,
centre of symmetry, translation, reflection, rotation
RESOURCES
2D shapes, protractors, pegboard and pegs, elastic
bands, 1-cm square dotted paper, 3D shapes, Pupil’s
Book page 19, scissors (for demonstrating angles).
• Draw the triangles on dotted paper and label
each one.
Teaching Input 1
o
2D shapes
• Measure the angles using the protractor.
Write the angle sizes on the drawing.
Hold up a rectangle.
• Can you tell me the properties of this
shape? For example, four right angles, opposite
sides are equal and parallel.
d
• Describe the angles (obtuse/acute), give
their measurements and name the triangle.
Repeat for a square, trapezium, rhombus,
triangle, hexagon, and so on.
• Would it be possible to make an equilateral
triangle?
• Can you tell me the properties of a
parallelogram?
• Can you tell me the properties of a kite?
• Can you name the different kinds of triangle?
Right-angled, isosceles, equilateral, scalene.
• Can you describe their properties?
Equilateral triangle – three sides the same length,
three equal angles.
Isosceles triangle – two sides the same length,
two equal angles.
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• Can you describe one of your triangles?
Teaching Input 2
o
3D shapes
Give each child a 3D shape and ask them to
describe the properties of the shape.
• What shape are the faces? How many
edges, vertices and right angles are there?
• Are any of the faces parallel?
Scalene triangle – no sides or angles the same.
• What is the name of your shape?
Right-angled triangle – one angle is a right angle.
• Can you tell me what symmetry is?
• Can you tell me what we mean by a ‘line of
symmetry’ or ‘axis of symmetry’?
protractors, pegboard and pegs, elastic
bands, 1-cm square dotted paper
• Can you give me an example in this room?
• Using the pegboard and elastic bands,
make a selection of triangles. Make sure
you include, a scalene, an isosceles and a
right-angled triangle.
• How many lines of symmetry are there in a
capital ‘A’? One line of symmetry. In a capital
‘H’? Two lines of symmetry. Make sure each
child gives an example.
YR5 pp02-43
21/3/01 4:08 pm
Page 35
REASONING ABOUT SHAPES
p
3D shapes
U N I T 17
Teaching Input 4
• Pick a shape.
• Write its name and properties. Write down
the number of faces, edges and vertices.
d
o
• What is an angle?
• Repeat for other shapes.
• What is a right angle?
• Design a table to display the information.
• Where could you find a right angle in the
classroom? Get the children to give several
examples.
• Which shapes have the same number of
faces? Edges? Vertices?
• How many degrees is a right angle?
• Can you explain to me what an obtuse
angle is?
Teaching Input 3
o
• Can you show me an example?
• Yesterday we discussed reflective
symmetry. Can anyone explain rotational
symmetry? Rotational symmetry is when you
can turn a shape around a point (centre of
symmetry) into one or more different positions
that look exactly the same.
• Can you tell me what an acute angle is?
• Can you show me an example? It may be
helpful to show angles using a pair of scissors.
• How many degrees is the angle formed by
a straight line?
On paper draw some angles. Ask the children
to estimate the angles and then measure them
– make sure each child takes a turn.
• Can anyone tell me what we do if we
translate a shape? Can you give me an
example? In a translation, the shape does not
turn – it slides from one position to another.
• Can you draw on the board any numbers or
letters that have lines of symmetry?
p
• Now swap your shapes with a partner.
• Do any of the letters or numbers have
rotational symmetry?
d
• Measure the angles inside your partner’s
shapes and label them.
• Add up all the angles in each shape and
write the total in the centre.
Pupil’s Book page 19
Ask the children to do the ‘Symmetry’
exercises from page 19 of the Pupil’s Book.
• How did you identify the different types of
symmetry?
protractors
• Design a shape for a new spacecraft! Draw
4-sided, 5-sided, 6-sided and 7-sided shapes.
• How many lines of symmetry do they have?
c
scissors (for demonstrating angles), paper
d
• What angles did your partner find in your
shapes?
• What did you discover?
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