Revision notes
Name flat shapes by their sides, tell the quadrilaterals apart, and find their lines of symmetry.
Chidi's kite, the football pitch at school and the STOP sign by the junction are all flat shapes. Each one has a name that tells you how many sides it has and what is special about it.
A plane shape is a flat shape you can draw on paper. A polygon is a plane shape made of straight sides joined end to end.
The name tells you the number of sides: triangle 3, quadrilateral 4, pentagon 5, hexagon 6, heptagon 7, octagon 8, nonagon 9, decagon 10.
A polygon is regular when all its sides are equal and all its angles are equal, like a STOP sign, which is a regular octagon.
🔑 Key idea: Count the sides, then match the prefix: tri 3, quad 4, penta 5, hexa 6, hepta 7, octa 8, nona 9, deca 10.
A square has 4 equal sides and 4 right angles. A rectangle has 4 right angles, with opposite sides equal.
A rhombus has 4 equal sides, but its angles need not be right angles. A parallelogram has two pairs of parallel sides, with opposite sides equal.
A trapezium has exactly one pair of parallel sides. A kite has two pairs of equal sides that are next to each other.
A square has everything a rectangle needs, so every square is also a special rectangle, but not every rectangle is a square.
🔑 Key idea: Check three things: equal sides, right angles and parallel sides.
A line of symmetry is a fold line where one half lands exactly on top of the other, like a mirror.
A rectangle has 2 lines of symmetry, a square has 4 and a kite has 1. A regular polygon has as many lines of symmetry as it has sides.
🔑 Key idea: Imagine folding the shape: if the halves match exactly, the fold is a line of symmetry.
A plane shape has 5 straight sides. What is it called?
Step 1: Match the number of sides
5 sides → pentagon
Why? "penta" means 5.
Answer: Pentagon
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