RAS question
What is the mirror image of the number 3218 when a mirror is placed on the right?
Correct answer: (D) 8123 (reversed and each digit laterally inverted).
With a mirror placed on the right, the number 3218 appears as 8123, with each digit laterally inverted.
Explanation
A right-side mirror gives a mirror image, not a simple rewrite of the number. The cited reasoning note defines a mirror image through lateral inversion: the left side becomes the right side, the right side becomes the left side, and the top and bottom stay unchanged. Applying that to 3218, the last digit is seen first, so the visible order becomes 8, 1, 2, 3. At the same time, each digit is horizontally flipped because the mirror changes left and right. That is why the required answer is the option representing 8123 with lateral inversion of the digits, not merely the typed number 8123.
Why the other options are wrong
- (A) A reverses the order to 8123 but leaves the digit shapes unchanged, whereas a mirror image requires lateral inversion as well.
- (B) B keeps 3218 unchanged, but a right-side mirror reverses left and right, so both the reading order and digit orientation change.
- (C) C gives 1832, which is not the right-to-left order of 3218 and also ignores the lateral inversion of each digit.
Concept
This tests non-verbal reasoning under mirror images, especially the distinction between reversal of order and lateral inversion. RAS repeats such questions because they quickly measure visual accuracy and rule-based spatial reasoning.