Flat shapes have sides and corners. Solid shapes have faces, edges and corners too — just in 3 dimensions. And every corner where two lines meet makes an angle with its own name.
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A triangle's 3 angles always add up to 180°, and a quadrilateral's 4 angles always add up to 360°.
Equilateral
all 3 sides equal
Isosceles
2 sides equal
Scalene
no sides equal
| Quadrilateral | What makes it special |
|---|---|
| Square | 4 equal sides, 4 right angles |
| Rectangle | opposite sides equal, 4 right angles |
| Rhombus | 4 equal sides, angles not always 90° |
| Trapezium | only 1 pair of parallel sides |
A solid shape has flat or curved faces, straight edges where two faces meet, and vertices (corners) where edges meet.
| Solid | Faces | Edges | Vertices |
|---|---|---|---|
| 🎲 Cube | 6 | 12 | 8 |
| 📦 Cuboid | 6 | 12 | 8 |
| 🏔️ Square pyramid | 5 | 8 | 5 |
| 🥫 Cylinder | 2 flat + 1 curved | 2 | 0 |
| 🍦 Cone | 1 flat + 1 curved | 1 | 1 |
| ⚽ Sphere | 1 curved | 0 | 0 |
An angle is measured in degrees. Its size decides what it is called.
Acute
less than 90°
Right
exactly 90°
Obtuse
between 90° and 180°
Straight
exactly 180°
🔑 Angle sums to remember
The 3 angles of any triangle always add up to 180°. The 4 angles of any quadrilateral always add up to 360°.
12 IMO-style questions on shapes, solids and angles. 🍀
