Sides and corners
A flat shape is named by its edges. Look at two things: whether the edges are straight or curved, and how many corners there are. A corner is a point where two straight sides meet.
The circle
A circle has one curved edge that goes all the way round and joins up with itself. It has no straight sides and no corners at all. Wheels, coins and the sun in a drawing are circles.
A circle: one curved edge, and no corners.
The triangle
A triangle has three straight sides, and they meet at three corners. Any shape with exactly three straight sides is a triangle, whether its sides are all the same length or not.
A triangle: three straight sides, and a dot at each of its three corners.
The square and the rectangle
A square and a rectangle both have four straight sides and four corners, and every corner is a square corner, like the corner of a page. What tells them apart is the length of the sides.
In a square, all four sides are the same length. In a rectangle, two sides are longer than the other two: the two long sides are opposite each other, and so are the two short sides. A door and a book cover are rectangles.
A square: four straight sides, all the same length, and four corners.
A rectangle: four straight sides and four corners. The top and bottom sides are longer than the two sides at the ends.
Count before you name
To name a shape, count its sides. No straight sides and one curved edge is a circle. Three sides is a triangle. Four sides is a square or a rectangle, and the lengths of the sides decide which.
The size of a shape and the way it is turned do not change its name. A tiny triangle is still a triangle, and so is a triangle that points down.
Worked example: A Train Picture Made of Circles, Rectangles and a Square
Question Ben makes a train picture from flat shapes. The 4 wheels are circles. The sun is a circle too. The 2 carriages are rectangles. The window is 1 square. (a) How many circles are in the picture? (b) How many shapes have straight sides?
1.Draw the picture. It has 4 wheels, 1 sun, 2 carriages and 1 window.
The picture has 4 wheels, 1 sun, 2 carriages and 1 window. 2.A circle is round and has no straight sides. The wheels and the sun are circles.
A circle is round and has no straight sides. The wheels and the sun are circles. 3.(a) Count the circles: 4 + 1 = 5. There are 5 circles in the picture.
(a) Count the circles: 4 + 1 = 5. There are 5 circles in the picture. 4.(b) The rectangles and the square have straight sides: 2 + 1 = 3. There are 3 shapes with straight sides.
(b) The rectangles and the square have straight sides: 2 + 1 = 3. There are 3 shapes with straight sides.
Answer: (a) 5 circles; (b) 3 shapes
Common mistakes
- Counting only the 4 wheels in part (a). The sun is a circle too, so there are 5 circles.
- Leaving out the window in part (b) because it is inside a carriage. The window is a square, and a square has straight sides.
More shapes and where they sit problems, worked step by step →
Worked example: The Odd One Out in a Group of Shapes
Question There are 5 shapes on a card: a square, a rectangle, a square standing on one corner, a triangle and a tall thin rectangle. All the shapes but one follow the same rule. (a) Which shape is the odd one out? (b) How many shapes follow the rule?
1.Count the sides of each shape. The square has 4 sides and the rectangle has 4 sides.
Count the sides of each shape. The square has 4 sides and the rectangle has 4 sides. 2.The square standing on one corner is still a square, so it has 4 sides. The tall thin rectangle has 4 sides too.
The square standing on one corner is still a square, so it has 4 sides. The tall thin rectangle has 4 sides too. 3.(a) The triangle has 3 sides. The rule is that a shape has 4 sides. The triangle is the odd one out.
(a) The triangle has 3 sides. The rule is that a shape has 4 sides. The triangle is the odd one out. 4.(b) Count the shapes with 4 sides: 1, 2, 3, 4. There are 4 shapes that follow the rule.
(b) Count the shapes with 4 sides: 1, 2, 3, 4. There are 4 shapes that follow the rule.
Answer: (a) the triangle, which has 3 sides; (b) 4 shapes
Common mistakes
- Picking the square standing on one corner because it looks different. It is still a square, and it has 4 sides.
- Picking the tall thin rectangle because of its size. The rule is about the number of sides, and it has 4 sides.
More shapes and where they sit problems, worked step by step →