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Which shape am I?
Discover Mathematics P2: Term 1, Lessons 41–50
GoalDescribe plane shapes by their clues and name a shape from its clues.
New words
clue · a hint that helps you find the answerdescribe · tell what a shape is likeclosed shape · a shape with no gaps in its edge
Explanation
In a ‘Which shape am I?’ game, one person gives clues and the other names the shape. Good clues are the number of sides, the number of vertices, whether the sides are equal, and whether a side is curved. ‘I have 3 vertices’ means a triangle. ‘I have 4 sides, two long and two short’ means a rectangle. A closed shape with straight sides needs at least 3 sides, so no shape has only 2 sides or only 2 vertices. A shape can have 10 sides, though, and it is easy to draw one.
Worked examples
Clue: ‘I have 3 vertices.’ Answer: a triangle. A triangle also has 3 sides.
Clues: ‘I have 4 sides and 4 vertices. Two sides are long and two are short.’ Answer: a rectangle.
Seif draws a closed shape with 10 straight sides. It is a 10-sided shape. Count its sides one by one to check.
Class activity
Riddle time. The child secretly picks one shape from the room’s windows, plates, books or pictures. Give three clues, one at a time, about sides, vertices and other attributes. The other person guesses. A good score is a correct guess after only two clues. Then swap.
Practice
1
I have 6 sides and 6 vertices. What shape am I?
A hexagon.
2
I have 4 equal sides and lean over like a diamond, and I am not a square. Which letter am I?
B, the rhombus.
3
Draw a closed shape with 8 straight sides. How many vertices does it have?
8 vertices. A closed shape has as many vertices as sides.
4
Can a closed shape with straight sides have only 2 sides? Why?
No. Two straight sides cannot close up. You need at least 3 sides.
5
Write two true clues for this shape.
Any two true clues, for example: 4 sides, 4 vertices, all sides equal.