One Is Mirrored
Read the puzzle
Six tiles, A to F, each show the same design: an L-shaped bar with one long arm and one short arm, plus a small triangle and a dot. From the bend of the L: A, long arm up (slightly left), short arm right; B, long arm down-left, short arm up-left; C, long arm right, short arm down; D, long arm up-right, short arm down-right; E, long arm left, short arm down; F, long arm down, short arm left. Five tiles are the design turned. Which tile is a mirror image?
Which tile is a mirror image?
E
Turn every tile upright: only E faces the wrong way.
How to solve it
Turning a shape never changes its handedness; only a mirror does. So pick one tile as the reference and check whether each other tile can be reached by turning it.
Step one: take A. From the bend, the long arm points up and the short arm points right. Walking out along the long arm, the short arm lies a quarter turn clockwise from it.
Step two: test the others the same way. C (long right, short down), F (long down, short left), B (long down-left, short up-left) and D (long up-right, short down-right) all have the short arm a quarter turn clockwise from the long arm, so they are A turned by different amounts.
Step three: E has the long arm pointing left and the short arm pointing down, which is a quarter turn anticlockwise. No amount of turning can swap that, so E is the mirror image.
The usual wrong answers are B and D, because their bars sit at a slant and look the most different. Slant is only a turn, not a flip.
Takeaway: ignore how tilted a tile looks and compare which way the short arm sits relative to the long one.
Learn the method: How to Solve Mental Rotation Puzzles: Turned or Mirrored?
