Question 1
Open this question's page →The grid below has 5 shaded squares, and a mirror stands along the dashed line MN on its right. Which figure is the mirror image of the grid?
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AnswerA · Figure 1
A mirror standing along MN, to the right of the grid, swaps left and right but not top and bottom: a square in column c moves to column and stays in its row.
So the shaded squares (1, 3), (1, 4), (1, 5), (2, 4), (2, 5) (row, column) move to (1, 1), (1, 2), (1, 3), (2, 1), (2, 2).
Figure 1 shows exactly these squares.
Worth noting
Figure 2 is the water image (top and bottom swapped), Figure 3 is the grid turned upside down, and Figure 4 is the grid given a quarter turn. A mirror never turns a figure; it only flips it.