Grade 4 Geometry: Lines of Symmetry

Worked examples

Real problems from the practice worksheets, solved one step at a time.

1. Example 1

   How many lines of symmetry does a regular pentagon have?

   1. A line of symmetry folds a shape into two halves that match exactly.
   2. Try a fold from each corner to the middle of the opposite side. Count its corners.
   3. So it has 5 lines of symmetry.

   Answer: 5

2. Example 2

   A shape is drawn on a number line and is symmetric about a fold line at 15. Corner P is at 11. At what number is the corner that matches P?

   1. In a symmetric shape, each point and its matching point are the same distance from the line of symmetry, on opposite sides.
   2. Corner P is 4 units to the left of 15. Go the same distance to the right of 15.
   3. 15 + 4 = 19, so the matching corner is at 19.

   Answer: 19

3. Example 3

   To draw the other half of a symmetric shape, Mia copies a corner that is 4 units from the line of symmetry. How many units apart are the corner and its copy?

   1. In a symmetric shape, each point and its matching point are the same distance from the line of symmetry, on opposite sides.
   2. The copy is also 4 units from the line, on the other side. Add the two distances.
   3. 4 + 4 = 8, so they are 8 units apart.

   Answer: 8 units