This unit requires students to enlarge and reduce the size of two-dimensional mathematical shapes by a scale factor. As students work in co-operative teams of four to complete a puzzle, they use a ruler, compass and protractor, and develop the ability to read and work through instructions to a finished product.
- follow instructions, in diagram form, to construct two-dimensional mathematical shapes, e.g. triangles, quadrilaterals, pentagons and hexagons
- enlarge and reduce two-dimensional mathematical shapes by a given scale factor
- identify invariant properties when enlarging and reducing two-dimensional mathematical shapes
- convert between mm and cm measurement.
- multiply whole numbers by a decimal
This unit moves students from knowing about two-dimensional mathematical shapes to being able to use them in a practical situation. The ability to accurately use a ruler, compass and protractor is the focus of the unit, along with the ability to read and work through instructions to a finished product.
This unit also introduces students to enlarging and reducing the size of two-dimensional mathematical shapes by a scale factor. Understanding what a scale factor is as well as how to work with scale factors in a practical situation are part of the unit, including invariant properties, i.e. aspects of shapes that remain the same when enlarged or reduced.
Scale factor is the amount a shape is enlarged or reduced. A scale factor of 2 means a shape doubles in size, with each length of each side doubling. A scale factor of 0.5 means the shape is halved in size. To find the length of a line changed by scale factor, the length is multiplied by the scale factor.
In this unit the centre of enlargement will not be considered.
Before this unit starts students need to know the following two-dimensional mathematical shapes and geometry vocabulary; equilateral triangle, right angle triangle, isosceles triangle, scalene triangle, quadrilateral, square, rectangle, trapezium, rhombus, parallelogram, pentagon, hexagon, octagon, perpendicular, parallel, right angle, base, interior angle, exterior angle.
Team puzzles and resources
quadrilateral, two-dimensional mathematical, enlarge, reduce, scale factor, invariant properties, convert, compass, intersecting point,
equilateral triangle, right angle triangle, isosceles triangle, scalene triangle, quadrilateral, square, rectangle, trapezium, rhombus, parallelogram, pentagon, hexagon, octagon, perpendicular, parallel, right angle, base, interior angle, exterior angle.
Arrange the students into teams of 4, explaining that this activity involves each team making four pieces of a puzzle, then putting the puzzle together. Each student works independently to start with making one piece of the puzzle. The shape of the piece is drawn as accurately as possible, checked by another team member, then cut out. Once all four pieces are made, they are put together to make a square or rectangle.
Use the copymaster of Team Puzzle One
Hand out the instructions for Team Puzzle One, one set for each team. Cut out the four sets of instructions, so each team member gets the instructions for an individual piece of the puzzle. The piece labelled number one, is the least challenging and number four is the most challenging in each puzzle. Some instructions are in diagram form and some written. If students are unsure of an instruction, the team needs to get together and work it out.
Students may need some teaching at this point, or before this activity starts, on how to use a compass to find the intersecting point of two lines of a set length. For example, How do you use a compass to draw a triangle with sides 10cm, 8cm and 6 cm long?
At the conclusion of this session when the puzzles have been completed, discuss with the class the activity.Topics that could be discussed are: the importance of accuracy, what to do if you are the first in your team to complete your piece, if you have trouble understanding an instruction, etc.
Over the next 2 or 3 days the teams work on the remaining team puzzles. The teacher’s role during this time is to encourage and teach students and teams as the need arises. At an appropriate time teaching is likely to be needed on enlarging and reducing by a scale factor. Team Puzzles Four, Five and Six have a scale factor to work out before the puzzles pieces are draw and cut out.
Have the students reflect and talk about the things they have learnt by completing these puzzles. Work on the puzzles the students have developed themselves.