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Paper Folding, Punched Holes & Mirror/Water Image
General Intelligence & Reasoning · Spatial & Non-verbal Reasoning
Useful for: SSC CGL
Overview
Mirror images reverse left and right; water images reverse top and bottom; punched holes multiply when the paper is unfolded.
Key points
- A mirror on the right side reverses left–right; top and bottom stay.
- A water image reverses top–bottom; left and right stay.
- Clock mirror time: subtract the time from 11:60 (e.g. 3:20 → 8:40).
- Each fold doubles the number of holes when unfolded.
- Letters symmetric about a vertical axis (A, H, I, M, O, T, U, V, W, X, Y) look the same in a mirror.
Explanation
- Letters symmetric about a horizontal axis (B, C, D, E, H, I, K, O, X) look the same in water.
- For folding, work backwards from the last fold to the first.
- Holes punched on the fold line produce holes centred on that line.
- Check the position of small details such as dots.
Step by step
- Decide mirror, water or fold.
- Apply the reversal or unfold.
- Check details.
Examples
- Mirror image of 3:20 on a clock shows 8:40.
- The mirror image of "TOM" keeps T, O and M looking the same but reverses their order to "MOT".
- Paper folded twice and punched once gives 4 holes when unfolded.
Traps and advanced points
- Trap: Reversing top–bottom in a mirror image.
- Trap: Forgetting the order reverses in a mirror word.
- Trap: Not doubling for each fold.
Quick revision
- Mirror: left–right; water: top–bottom.
- Clock mirror = 11:60 − time.
- Holes double per fold.
Practice MCQs
A square paper is folded once and one hole is punched through both layers. How many holes appear when it is unfolded?
- 4
- 1
- 3
- 2
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Answer: (d) 2. Each layer gets one hole.
A paper is folded twice into a quarter and one hole is punched. How many holes appear on unfolding?
- 4
- 2
- 3
- 8
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Answer: (a) 4. Four layers are punched together.
A clock shows 3:15. What time does its mirror image show?
- 8:45
- 9:45
- 3:45
- 9:15
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Answer: (a) 8:45. Mirror time = 11:60 − 3:15 = 8:45.
The mirror image (vertical mirror) of the small letter 'b' looks like
- q
- p
- d
- b
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Answer: (c) d. A side mirror flips left and right.
The water image of the small letter 'b' looks like
- p
- d
- q
- b
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Answer: (a) p. Water reflection flips top and bottom.
Which word looks exactly the same in a vertical mirror?
- DAD
- MOM
- BOB
- NUN
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Answer: (b) MOM. M and O are symmetric left to right, and the word reads the same backwards.
More topics in this chapter
Notes and questions are written by Kundali IQ for practice. They are not official papers; always check the latest official notification for the syllabus and pattern.