In this guide
Image questions look like they need a good eye. They don't. They need one rule applied without hurry: a mirror flips left and right, and water flips top and bottom. Candidates lose these marks by trusting the first option that "looks right" instead of checking one feature at a time.
Expect them in the reasoning section as figure questions ("Which option is the mirror image of the given figure?"), as letter and number strings, and as clock questions. They take under a minute once the rules are automatic.
The two reflections
| Reflection | Where the mirror is | What swaps | What stays |
|---|---|---|---|
| Mirror image | A vertical line beside the figure | Left ↔ right | Top and bottom |
| Water image | A horizontal line below the figure | Top ↔ bottom | Left and right |
| Both, one after the other | — | Both | Nothing; the result is the figure turned through 180° |
Some questions draw the mirror as a line MN. The rule depends on the line, not the word: a mirror placed below or above the figure behaves like water.
Letters and digits that do not change
A letter looks the same in a mirror if it is symmetric about a vertical line through its middle. It looks the same in water if it is symmetric about a horizontal line.
| Reflection | Capital letters that look the same | Digits (plain block style) |
|---|---|---|
| Mirror | A, H, I, M, O, T, U, V, W, X, Y | 0, 1, 8 |
| Water | B, C, D, E, H, I, K, O, X | 0, 1, 3, 8 |
| Both | H, I, O, X | 0, 1, 8 |
Digit shapes vary a little between fonts (a 1 with a base stroke is not symmetric), so treat the digit column as a guide and look at the figure you are given.
Words and number strings
In a mirror, two things happen to a word: the letters appear in reverse order, and each letter is flipped left to right. So a word looks unchanged in a mirror only if it reads the same backwards and every letter is mirror-symmetric. WOW and TOOT qualify. NOON does not, because N is not symmetric.
In water, the order stays the same and each letter turns upside down. So a word looks unchanged in water if every letter is on the water list. CHOICE, BOX and HIDE all qualify.
Worked question. Which word looks the same in its water image? (a) CHOICE (b) MOTHER (c) TOWER (d) BUCKET
C, H, O, I, C and E are all on the water list. MOTHER has M, T and R; TOWER has T, W and R; BUCKET has U and T. Answer: (a) CHOICE.
For a number string such as 2 7 4 in a mirror, the digits appear as 4 7 2, each facing the other way. In the options, first check the order, then check that the asymmetric digits (2, 4, 7) are reversed.
Figures described on a grid
Picture the figure in a 3 × 3 grid. A mirror swaps the left and right columns; the middle column stays. Water swaps the top and bottom rows; the middle row stays. An arrow also changes direction:
| Arrow points | In a mirror | In water |
|---|---|---|
| Up | Up | Down |
| Right | Left | Right |
| North-east | North-west | South-east |
| South-west | South-east | North-west |
Worked question. A figure has a black dot in the top-left cell, an arrow in the centre pointing north-east, and a small square in the bottom-right cell. Describe its mirror image and its water image.
- Mirror: dot in the top-right cell; arrow pointing north-west; square in the bottom-left cell.
- Water: dot in the bottom-left cell; arrow pointing south-east; square in the top-right cell.
To pick an option, choose one distinctive element (the dot), work out where it must be, and strike out every option where it is wrong. Then check a second element (the arrow's direction) on what remains. Options are often built so that three of them get one element right.
Clocks in a mirror
A mirror image of a clock shows:
Mirror time = 11:60 − actual time
The subtraction works because the hands' positions are reflected about the 12–6 line. Writing 12:00 as 11:60 simply saves a borrowing step.
- Actual 2:25 → 11:60 − 2:25 = 9:35.
- Actual 7:50 → 11:60 − 7:50 = 4:10.
- Actual 3:00 → 11:60 − 3:00 = 8:60 = 9:00.
- For times from 12:01 to 12:59, use 23:60: actual 12:20 → 23:60 − 12:20 = 11:40.
The rule works both ways. If the mirror shows 4:35, the actual time is 11:60 − 4:35 = 7:25. The only times that look the same in a mirror are 12:00 and 6:00.
Clocks in water
For water images, the usual exam convention is 18:30 − actual time, then subtract 12 if the answer is more than 12. Actual 4:10 → 14:20 → 2:20. Actual 8:20 → 10:10.
Practice
- Which of these letters look the same in a mirror: B, H, K, U, Z?
- A clock shows 3:15. What does its mirror image show?
- A clock shows 10:40. What does its mirror image show?
- Which of these letters look the same in water: A, C, E, M, T?
- Which word looks the same in a mirror? (a) WOW (b) NOON (c) KAYAK (d) RADAR
- The mirror image of a clock shows 9:50. What is the actual time?
- A figure has a shaded triangle in the bottom-left cell and an arrow in the top-middle cell pointing east. Describe its water image.
- Using the exam convention, what does the water image of a clock show at 7:10?
Answers:
- H and U. Both are symmetric about a vertical line. B, K and Z are not.
- 8:45. 11:60 − 3:15.
- 1:20. 11:60 − 10:40.
- C and E. Both are symmetric about a horizontal line. A, M and T are not.
- (a) WOW. It reads the same backwards, and W and O are mirror-symmetric. N, K, R and D are not.
- 2:10. The rule works in reverse: 11:60 − 9:50.
- Triangle in the top-left cell; arrow in the bottom-middle cell, still pointing east. Water swaps top and bottom only.
- 11:20. 18:30 − 7:10.
What to do next
- Write the mirror and water letter lists from memory until you can do it in 30 seconds.
- Solve 15 mirror-clock questions in one sitting; the subtraction should become automatic.
- Move on to paper folding and cutting, which uses the same reflection idea across fold lines.
- Revise the clock angle method in clocks and calendars.
A note on dates and numbers. Exam patterns, vacancies and schedules change from year to year. Always confirm the current details in the latest notification on the Staff Selection Commission website .
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