A Quarter Turn
Read the puzzle
A square card shows a 3 by 3 grid of cells, gold (1) or dark (0). Rows, top to bottom: 110, 001, 011. The card is given a quarter turn clockwise. Which card do you get? A: 011, 101, 100. B: 110, 001, 011. C: 001, 101, 110. D: 100, 101, 011.
Which card do you get?
Clockwise means the way clock hands move.
C
Clockwise, the left column becomes the top row. Card C.
How to solve it
For a quarter turn clockwise, each column becomes a row. The left column, read from bottom to top, becomes the new top row; the middle column, bottom to top, becomes the middle row; the right column, bottom to top, becomes the bottom row.
Left column, bottom to top: dark, dark, gold, so the top row is dark, dark, gold. Middle column: gold, dark, gold, so the middle row is gold, dark, gold. Right column: gold, gold, dark, so the bottom row is gold, gold, dark. That is card C.
The usual mistake is turning the wrong way. A quarter turn anticlockwise gives card A. B is the card not turned at all, and D is a flip across the diagonal from top left to bottom right.
Quick check: the gold top-left cell must land at the top right, and the gold cell in the middle of the right edge must land in the middle of the bottom edge. A fails the second test and D fails the first; only C passes both.
Learn the method: How to Solve Mental Rotation Puzzles: Turned or Mirrored?
