Symmetry

A line of symmetry is a line drawn through a picture such that each side is a mirror image of the other.

A. Symmetric	B. Not Symmetric	C. Not Symmetric

Look at figure A. Can you see that if you flipped one side across the line you get an exact match?

Compare where the line is in Figure A to where it is in Figure B. In Figure B the left side is clearly different from the right side.

How about Figure C. Both sides are approximately the same size. However, merely flipping one side to the other would not produce a duplicate.

Animating the figures would help this explanation. I could show the flipping of one side over and show that the two are the same/different.