CAMBRIDGE LOWER SECONDARY MATHEMATICS 7: TEACHER’S RESOURCE

Additional teaching
ideas
8.2 Circles and polygons
Starter idea Description: Learners can read the instructions
and start their answer. Walk around the class. Ask
Line symmetry and rotational symmetry learners what their reasons are for the groups they
of polygons (5–10 minutes) are using. It is important to encourage the more
Resources: Electronic whiteboard or suite of confident learners to group with better reasons than
computers/tablets ‘they have four sides’ or ‘they’re all triangles’.

Description: The aim of this activity is to help Answers: For example: quadrilaterals; triangles;
learners know the number of lines of symmetry and regular polygons [must include the square]; number
order of rotational symmetry of common shapes. of sides = number of lines of symmetry; number of
Enter ‘transum.org polygons’ into a search engine. sides = order of rotational symmetry; number of
When directed to the page, learners answer the lines of symmetry = order of rotational symmetry;
‘Line Symmetry’ tab first and then the ‘Rotational no lines of symmetry; rotational symmetry of
Symmetry’. This ‘drag and drop’ resource does not order 1; rotational symmetry of order 2; rotational
tell learners which questions they have answered symmetry of more than order 4, etc.
incorrectly. It just tells them how many mistakes they
have made. Differentiation ideas: For more confident classes, list
If you have enough computers/tablets available, it is a few of the easier reasons given in the answers that
a good idea for learners to complete this individually. they are not allowed to use. This should make them
Alternatively, as a class, learners could, in turn, think more deeply about the properties and use more
choose a shape to use or a word to drag. Other interesting groups.
learners could then vote true/not true before moving
on. Learners must answer all questions before they Snap! (5–10 minutes (set a time limit))
can use the auto-check. Learning intention: To recall symmetry facts for
Learners can attempt only the questions in one tab. quadrilaterals and triangles.
They do not have to attempt both tabs, but it is a Resources: Resource sheet 8.2a
good idea to check their understanding during one of Description: Only learners with a good understanding
the starter activities. of the information given in the diagrams in this
This is a free resource and learners can access this section can play this game of Snap!.
too. They might wish to practise at home, so make Ask learners to work in pairs. Print copies of
sure they write down the web address of this excellent Resource sheet 8.2a onto thick paper. Cut sets of
resource. There are many other similar resources cards from the resource sheet. Distribute a shuffled
available. set of cards to each pair of learners playing the game.

Main teaching ideas The object of the game is to find matching pairs
of cards.
Question 10 (5–15 minutes) One learner deals the shuffled cards into two piles,
Learning intention: To think about why some shapes with the cards placed face down.
have similar properties to other shapes. To think
The other learner goes first and the play then
about the properties of shapes to try to reason why
alternates.
they should be grouped.
Resources: Notebooks, Learner’s Book

1 Cambridge Lower Secondary Mathematics 7 – Byrd, Byrd & Pearce © Cambridge University Press 2021
 CAMBRIDGE LOWER SECONDARY MATHEMATICS 7: TEACHER’S RESOURCE

On their turn, each learner turns over the top card Differentiation ideas: Two pairs could play this
from their face-down pile and places it to the side of game together; that is, one pair playing against
their other cards. another pair.
When a learner turns over a card that matches a card
already face up on the other learner’s pile, they race Plenary idea
to be the first to call ‘Snap!’.
Polygon sketch (5 minutes)
The learner who calls ‘Snap!’ first wins both piles and Resources: Notebooks or mini whiteboards
adds them to the bottom of their face-down pile.
Description: Ask learners to sketch, in order, a
When moving a card from their face-down pile to rhombus, a parallelogram, a square, a hexagon, an
their face-up pile, each learner should turn the card octagon, a pentagon and a heptagon (and any other
away from themselves. This ensures that the learner shapes you think they need to practise).
does not see the card before their partner sees it. (The
learner should also turn the card quickly, so that When they have drawn all the shapes, ask ‘Which
their partner does not see the card first.) shapes are the easiest to draw?’, ‘What makes the
pentagon and heptagon harder to draw than a
The game continues until one learner has no cards hexagon?’, ‘How accurate are your drawings?’ and
left. The winner is the learner with all the cards at ‘Are they accurate enough?’
the end of play or with more cards at the end of a
set time. Assessment ideas: Learners can either show you
their sketches (if they are on a mini whiteboard)
Resource sheet 8.2b shows the matching pairs. You or show a partner their sketches (if they are in a
could distribute this sheet at the end of the game as notebook).
an answer sheet.

Answers: See Resource sheet 8.2b.

2 Cambridge Lower Secondary Mathematics 7 – Byrd, Byrd & Pearce © Cambridge University Press 2021