Symmetry · Grade 4
In Grade 4 you learn: symmetry in shapes and pictures; lines of symmetry; completing symmetric figures.
A shape has line symmetry if it can be folded so that the two halves match exactly. It has rotational symmetry if it looks the same after a turn of less than 360°. Symmetry appears in logos, flowers, snowflakes and road signs.
Key facts
- A line of symmetry is a mirror line: each point has a matching point the same distance away on the other side.
- Square 4 lines; rectangle 2; rhombus 2; kite 1; parallelogram 0 (but order 2).
- The smallest turn that fits a shape onto itself is 360° ÷ order.
Worked examples
Example 1
How many lines of symmetry does a rectangle have?
Answer: 2