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SSC CGL Reasoning · Mirror and Water Images

Letters and Numbers in a Mirror

A string of letters, numbers and symbols seen in a mirror beside it (the order reverses and each character flips) or in a mirror below it, a water image (the order stays and each character turns upside down).

All Mirror and Water Images notes

Why this matters

Sixty-five questions in the bank, 23 from the 2023 shifts and 42 from the 2024 shifts, with 50 EASY and 15 MODERATE. The options differ in one or two characters, so knowing which characters change in a mirror and which do not finds the answer in seconds.

Concept 1 of 3: Which characters change in a mirror

A character that is the same on its left and right halves looks unchanged in a mirror beside it. A character that is the same on its top and bottom halves looks unchanged in a mirror below it. Every other character comes out reversed, and that is where the options differ.

Definition

  • Unchanged in a mirror beside it (left to right): the capitals A, H, I, M, O, T, U, V, W, X, Y; the small letters i, l, o, v, w, x; the digits 0 and 8.
  • Unchanged in a mirror below it (top to bottom): the capitals B, C, D, E, H, I, K, O, X; the digits 0, 3 and 8.
  • Pairs that swap: in a mirror beside, b and d swap, and p and q swap. In a mirror below, b and p swap, and d and q swap.
  • Any other character (R, F, N, 2, 4, 7 and so on) comes out reversed, and it does not turn into another character.
  • Fast route: look only at the characters that change. The options are built to differ there.

Worked example

Which characters of the string R8HL2 look exactly the same in a mirror placed beside it?
Practice this conceptself-check · 4 quick reps

Calling a character unchanged when only its outline is close

N and S look nearly balanced, but in a mirror beside them they come out reversed. Check that the left half truly matches the right half before you call a character unchanged.

Using the wrong list for the mirror

B looks the same in a mirror below it but reversed in a mirror beside it; A is the other way round. Pick the list that matches where the mirror stands.

Concept 2 of 3: A mirror beside the string

A mirror on the right (or the left) of a string does two things at once. The character nearest the mirror comes first, so the order reverses. And every character is seen from behind, so each one flips left to right.

Definition

1. Write the characters in reverse order: the last one comes first. 2. Flip each character left to right. Characters that are the same on both sides stay as they are. 3. Top and bottom never change in a mirror beside the string: nothing turns upside down.

  • A mirror on the left gives the same image as a mirror on the right.
  • Fast route: first strike any option that is not in reverse order. Then look at the first and last characters of each option that is left, and at any character that is not the same on both sides.

Worked example

A mirror stands on the right of the string FAN32. How does the image read from left to right?
Practice this conceptself-check · 4 quick reps

The same idea in a real exam question:

SSC CGL · 2024 · Tier I, 10 Sep 2024, Shift 1 · Q2Easy

Example 2 · Mirror and Water Images · Letters and Numbers in a Mirror

Select the correct mirror image of the given figure when the mirror is placed at MN as shown below.

Reversing the order but not the characters

An option with the right order and a 2, 3 or R printed the normal way is wrong. Each character that is not the same on both sides must come out reversed.

Flipping the characters but keeping the order

An option that keeps the original order and reverses every character is neither a mirror image nor a water image. In a mirror beside the string the order must reverse as well.

Turning a character upside down

A mirror beside the string never swaps top and bottom. An option where u has become n, or A stands on its point, is a water image, not a mirror image.
Drill 61 more on a mirror beside the string

Concept 3 of 3: A mirror below: the water image

A mirror lying below a string, like the surface of water, shows it upside down. The characters keep their order from left to right, and each one flips top to bottom.

Definition

1. Keep the order of the characters. 2. Turn each one upside down by flipping it top to bottom. Characters that are the same at top and bottom (B, C, D, E, H, I, K, O, X, 0, 3, 8) stay as they are.

  • A flip is not a turn: 6 flipped top to bottom is not 9. A 9 is a 6 turned round half a circle, which a mirror never does.
  • Fast route: check the characters that are not the same at top and bottom first, and strike any option that has turned one round instead of flipping it.

Worked example

A mirror lies below the string CODE5. What does the water image show?
Practice this conceptself-check · 4 quick reps

The same idea in a real exam question:

SSC CGL · 2023 · Tier I, 20 Jul 2023, Shift 1 · Q22Easy

Example 3 · Mirror and Water Images · Letters and Numbers in a Mirror

Select the correct mirror image of the given combination when the mirror is placed at 'PQ' as shown. DA67Yb

Turning instead of flipping

Turning a 6 half a circle gives a 9, and turning b gives q. A water image flips each character top to bottom, so 6 becomes a shape with its loop at the top and b becomes p.

Reversing the order in a water image

Only a mirror beside the string reverses the order. A mirror below it keeps the left-to-right order exactly as printed.
Drill 2 more on a mirror below: the water image

Summary — formulas & gotchas at a glance

A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.

Watch out for (7)

Test yourself on Mirror and Water Images

20 past SSC CGL questions from this chapter, timed at 12 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.

Take the Mirror and Water Images chapter testDrill all 65 questions