Single Horizontal Fold - Basic - Absolute-Beginner Level: core concept mastery Single Horizontal Fold - Basic ABSOLUTE BEGINNER

This skill primer 🌟 worksheet focuses on Single Horizontal Fold - Basic - a key topic in Paper Folding. You'll solve 20 absolute-beginner-level problems (Worksheet 1 of 10). The primary focus is on core concept mastery. Master single horizontal fold - basic problems, single horizontal fold - basic reasoning questions, and single horizontal fold - basic practice through systematic practice.

📝 Worksheet 1 of 10 • 20 questions • ⏱️ Estimated time: 20 minutes • 🎯 Absolute Beginner level

What you'll learn in this worksheet:
Your progress through Single Horizontal Fold - Basic
Worksheet 1 of 10 (0% complete)

Question 1

A square sheet of paper is folded horizontal (top to bottom). A hole is punched at the center of folded paper. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Analysis:
- Starting with a square paper (transparent sheet)
- Performing a horizontal (top to bottom) fold
- This creates 2 layers of paper stacked vertically

Step 2 - Understanding the Fold:
- A horizontal fold creates a mirror line across the middle
- Any hole punched will appear on both layers
- The symmetry axis is horizontal, but hole alignment becomes vertical

Step 3 - Hole Punch Visualization:
- Hole location: center of folded paper
- When punched, it goes through both layers simultaneously
- Each layer will have the hole at the same relative position from the fold

Step 4 - Mental Unfolding:
- Unfold the paper back to original position
- The hole on the top layer stays in place (center)
- The hole on the bottom layer mirrors across the fold line
- Result: Two holes vertically aligned in the center

Step 5 - Verification:
- Check symmetry: Holes should be mirror images across horizontal center line
- Count: Single punch through 2 layers = 2 holes when unfolded
- Pattern matches: Two holes vertically aligned in the center

Mental Visualization Tip: Imagine tracing the fold line and reflecting the hole position across it like a mirror reflection.

Common Mistake to Avoid: Don't confuse horizontal and vertical fold patterns - horizontal folds create vertical symmetry in hole patterns.

Question 2

A square sheet of paper is folded horizontal (top to bottom). A hole is punched at the center of folded paper. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Analysis:
- Starting with a square paper (transparent sheet)
- Performing a horizontal (top to bottom) fold
- This creates 2 layers of paper stacked vertically

Step 2 - Understanding the Fold:
- A horizontal fold creates a mirror line across the middle
- Any hole punched will appear on both layers
- The symmetry axis is horizontal, but hole alignment becomes vertical

Step 3 - Hole Punch Visualization:
- Hole location: center of folded paper
- When punched, it goes through both layers simultaneously
- Each layer will have the hole at the same relative position from the fold

Step 4 - Mental Unfolding:
- Unfold the paper back to original position
- The hole on the top layer stays in place (center)
- The hole on the bottom layer mirrors across the fold line
- Result: Two holes vertically aligned in the center

Step 5 - Verification:
- Check symmetry: Holes should be mirror images across horizontal center line
- Count: Single punch through 2 layers = 2 holes when unfolded
- Pattern matches: Two holes vertically aligned in the center

Mental Visualization Tip: Imagine tracing the fold line and reflecting the hole position across it like a mirror reflection.

Common Mistake to Avoid: Don't confuse horizontal and vertical fold patterns - horizontal folds create vertical symmetry in hole patterns.

Question 3

A square sheet of paper is folded horizontal (bottom to top). A hole is punched at the near the folded edge. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Setup:
- Square paper folded horizontally from bottom to top
- Creates 2 overlapping layers
- Fold line is at the horizontal center

Step 2 - Fold Mechanics:
- Bottom half folds upward to cover top half
- Both layers are identical in size and shape
- Perfect alignment creates clean symmetry

Step 3 - Punch Location Analysis:
- Hole position: near the folded edge
- In folded state: appears close to the physical edge
- When unfolded: will appear near the center line

Step 4 - Unfolding Process:
- Carefully unfold along the horizontal crease
- Top layer hole remains at punch location
- Bottom layer hole mirrors across center line
- Result: Two holes close together near center horizontal line

Step 5 - Geometric Confirmation:
- Distance from center: equal for both holes
- Vertical alignment: both holes at same x-coordinate
- Pattern: symmetric about horizontal axis

Spatial Reasoning Technique:
Use coordinate geometry - if hole is at (x,y) on folded paper, unfolded positions are (x,y) and (x,100-y) for 100x100 paper.

Key Insight: The folded edge becomes the symmetry line when unfolded.

Question 4

A square sheet of paper is folded horizontal (bottom to top). A hole is punched at the near the folded edge. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Setup:
- Square paper folded horizontally from bottom to top
- Creates 2 overlapping layers
- Fold line is at the horizontal center

Step 2 - Fold Mechanics:
- Bottom half folds upward to cover top half
- Both layers are identical in size and shape
- Perfect alignment creates clean symmetry

Step 3 - Punch Location Analysis:
- Hole position: near the folded edge
- In folded state: appears close to the physical edge
- When unfolded: will appear near the center line

Step 4 - Unfolding Process:
- Carefully unfold along the horizontal crease
- Top layer hole remains at punch location
- Bottom layer hole mirrors across center line
- Result: Two holes close together near center horizontal line

Step 5 - Geometric Confirmation:
- Distance from center: equal for both holes
- Vertical alignment: both holes at same x-coordinate
- Pattern: symmetric about horizontal axis

Spatial Reasoning Technique:
Use coordinate geometry - if hole is at (x,y) on folded paper, unfolded positions are (x,y) and (x,100-y) for 100x100 paper.

Key Insight: The folded edge becomes the symmetry line when unfolded.

Question 5

A square sheet of paper is folded horizontal (top to bottom). A hole is punched at the center of folded paper. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Analysis:
- Starting with a square paper (transparent sheet)
- Performing a horizontal (top to bottom) fold
- This creates 2 layers of paper stacked vertically

Step 2 - Understanding the Fold:
- A horizontal fold creates a mirror line across the middle
- Any hole punched will appear on both layers
- The symmetry axis is horizontal, but hole alignment becomes vertical

Step 3 - Hole Punch Visualization:
- Hole location: center of folded paper
- When punched, it goes through both layers simultaneously
- Each layer will have the hole at the same relative position from the fold

Step 4 - Mental Unfolding:
- Unfold the paper back to original position
- The hole on the top layer stays in place (center)
- The hole on the bottom layer mirrors across the fold line
- Result: Two holes vertically aligned in the center

Step 5 - Verification:
- Check symmetry: Holes should be mirror images across horizontal center line
- Count: Single punch through 2 layers = 2 holes when unfolded
- Pattern matches: Two holes vertically aligned in the center

Mental Visualization Tip: Imagine tracing the fold line and reflecting the hole position across it like a mirror reflection.

Common Mistake to Avoid: Don't confuse horizontal and vertical fold patterns - horizontal folds create vertical symmetry in hole patterns.

Question 6

A square sheet of paper is folded horizontal (top to bottom). A hole is punched at the center of folded paper. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Analysis:
- Starting with a square paper (transparent sheet)
- Performing a horizontal (top to bottom) fold
- This creates 2 layers of paper stacked vertically

Step 2 - Understanding the Fold:
- A horizontal fold creates a mirror line across the middle
- Any hole punched will appear on both layers
- The symmetry axis is horizontal, but hole alignment becomes vertical

Step 3 - Hole Punch Visualization:
- Hole location: center of folded paper
- When punched, it goes through both layers simultaneously
- Each layer will have the hole at the same relative position from the fold

Step 4 - Mental Unfolding:
- Unfold the paper back to original position
- The hole on the top layer stays in place (center)
- The hole on the bottom layer mirrors across the fold line
- Result: Two holes vertically aligned in the center

Step 5 - Verification:
- Check symmetry: Holes should be mirror images across horizontal center line
- Count: Single punch through 2 layers = 2 holes when unfolded
- Pattern matches: Two holes vertically aligned in the center

Mental Visualization Tip: Imagine tracing the fold line and reflecting the hole position across it like a mirror reflection.

Common Mistake to Avoid: Don't confuse horizontal and vertical fold patterns - horizontal folds create vertical symmetry in hole patterns.

Question 7

A square sheet of paper is folded horizontal (top to bottom). A hole is punched at the center of folded paper. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Analysis:
- Starting with a square paper (transparent sheet)
- Performing a horizontal (top to bottom) fold
- This creates 2 layers of paper stacked vertically

Step 2 - Understanding the Fold:
- A horizontal fold creates a mirror line across the middle
- Any hole punched will appear on both layers
- The symmetry axis is horizontal, but hole alignment becomes vertical

Step 3 - Hole Punch Visualization:
- Hole location: center of folded paper
- When punched, it goes through both layers simultaneously
- Each layer will have the hole at the same relative position from the fold

Step 4 - Mental Unfolding:
- Unfold the paper back to original position
- The hole on the top layer stays in place (center)
- The hole on the bottom layer mirrors across the fold line
- Result: Two holes vertically aligned in the center

Step 5 - Verification:
- Check symmetry: Holes should be mirror images across horizontal center line
- Count: Single punch through 2 layers = 2 holes when unfolded
- Pattern matches: Two holes vertically aligned in the center

Mental Visualization Tip: Imagine tracing the fold line and reflecting the hole position across it like a mirror reflection.

Common Mistake to Avoid: Don't confuse horizontal and vertical fold patterns - horizontal folds create vertical symmetry in hole patterns.

Question 8

A square sheet of paper is folded horizontal (bottom to top). A hole is punched at the near the folded edge. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Setup:
- Square paper folded horizontally from bottom to top
- Creates 2 overlapping layers
- Fold line is at the horizontal center

Step 2 - Fold Mechanics:
- Bottom half folds upward to cover top half
- Both layers are identical in size and shape
- Perfect alignment creates clean symmetry

Step 3 - Punch Location Analysis:
- Hole position: near the folded edge
- In folded state: appears close to the physical edge
- When unfolded: will appear near the center line

Step 4 - Unfolding Process:
- Carefully unfold along the horizontal crease
- Top layer hole remains at punch location
- Bottom layer hole mirrors across center line
- Result: Two holes close together near center horizontal line

Step 5 - Geometric Confirmation:
- Distance from center: equal for both holes
- Vertical alignment: both holes at same x-coordinate
- Pattern: symmetric about horizontal axis

Spatial Reasoning Technique:
Use coordinate geometry - if hole is at (x,y) on folded paper, unfolded positions are (x,y) and (x,100-y) for 100x100 paper.

Key Insight: The folded edge becomes the symmetry line when unfolded.

Question 9

A square sheet of paper is folded horizontal (bottom to top). A hole is punched at the near the folded edge. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Setup:
- Square paper folded horizontally from bottom to top
- Creates 2 overlapping layers
- Fold line is at the horizontal center

Step 2 - Fold Mechanics:
- Bottom half folds upward to cover top half
- Both layers are identical in size and shape
- Perfect alignment creates clean symmetry

Step 3 - Punch Location Analysis:
- Hole position: near the folded edge
- In folded state: appears close to the physical edge
- When unfolded: will appear near the center line

Step 4 - Unfolding Process:
- Carefully unfold along the horizontal crease
- Top layer hole remains at punch location
- Bottom layer hole mirrors across center line
- Result: Two holes close together near center horizontal line

Step 5 - Geometric Confirmation:
- Distance from center: equal for both holes
- Vertical alignment: both holes at same x-coordinate
- Pattern: symmetric about horizontal axis

Spatial Reasoning Technique:
Use coordinate geometry - if hole is at (x,y) on folded paper, unfolded positions are (x,y) and (x,100-y) for 100x100 paper.

Key Insight: The folded edge becomes the symmetry line when unfolded.

Question 10

A square sheet of paper is folded horizontal (top to bottom). A hole is punched at the center of folded paper. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Analysis:
- Starting with a square paper (transparent sheet)
- Performing a horizontal (top to bottom) fold
- This creates 2 layers of paper stacked vertically

Step 2 - Understanding the Fold:
- A horizontal fold creates a mirror line across the middle
- Any hole punched will appear on both layers
- The symmetry axis is horizontal, but hole alignment becomes vertical

Step 3 - Hole Punch Visualization:
- Hole location: center of folded paper
- When punched, it goes through both layers simultaneously
- Each layer will have the hole at the same relative position from the fold

Step 4 - Mental Unfolding:
- Unfold the paper back to original position
- The hole on the top layer stays in place (center)
- The hole on the bottom layer mirrors across the fold line
- Result: Two holes vertically aligned in the center

Step 5 - Verification:
- Check symmetry: Holes should be mirror images across horizontal center line
- Count: Single punch through 2 layers = 2 holes when unfolded
- Pattern matches: Two holes vertically aligned in the center

Mental Visualization Tip: Imagine tracing the fold line and reflecting the hole position across it like a mirror reflection.

Common Mistake to Avoid: Don't confuse horizontal and vertical fold patterns - horizontal folds create vertical symmetry in hole patterns.

Question 11

A square sheet of paper is folded horizontal (bottom to top). A hole is punched at the near the folded edge. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Setup:
- Square paper folded horizontally from bottom to top
- Creates 2 overlapping layers
- Fold line is at the horizontal center

Step 2 - Fold Mechanics:
- Bottom half folds upward to cover top half
- Both layers are identical in size and shape
- Perfect alignment creates clean symmetry

Step 3 - Punch Location Analysis:
- Hole position: near the folded edge
- In folded state: appears close to the physical edge
- When unfolded: will appear near the center line

Step 4 - Unfolding Process:
- Carefully unfold along the horizontal crease
- Top layer hole remains at punch location
- Bottom layer hole mirrors across center line
- Result: Two holes close together near center horizontal line

Step 5 - Geometric Confirmation:
- Distance from center: equal for both holes
- Vertical alignment: both holes at same x-coordinate
- Pattern: symmetric about horizontal axis

Spatial Reasoning Technique:
Use coordinate geometry - if hole is at (x,y) on folded paper, unfolded positions are (x,y) and (x,100-y) for 100x100 paper.

Key Insight: The folded edge becomes the symmetry line when unfolded.

Question 12

A square sheet of paper is folded horizontal (top to bottom). A hole is punched at the center of folded paper. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Analysis:
- Starting with a square paper (transparent sheet)
- Performing a horizontal (top to bottom) fold
- This creates 2 layers of paper stacked vertically

Step 2 - Understanding the Fold:
- A horizontal fold creates a mirror line across the middle
- Any hole punched will appear on both layers
- The symmetry axis is horizontal, but hole alignment becomes vertical

Step 3 - Hole Punch Visualization:
- Hole location: center of folded paper
- When punched, it goes through both layers simultaneously
- Each layer will have the hole at the same relative position from the fold

Step 4 - Mental Unfolding:
- Unfold the paper back to original position
- The hole on the top layer stays in place (center)
- The hole on the bottom layer mirrors across the fold line
- Result: Two holes vertically aligned in the center

Step 5 - Verification:
- Check symmetry: Holes should be mirror images across horizontal center line
- Count: Single punch through 2 layers = 2 holes when unfolded
- Pattern matches: Two holes vertically aligned in the center

Mental Visualization Tip: Imagine tracing the fold line and reflecting the hole position across it like a mirror reflection.

Common Mistake to Avoid: Don't confuse horizontal and vertical fold patterns - horizontal folds create vertical symmetry in hole patterns.

Question 13

A square sheet of paper is folded horizontal (bottom to top). A hole is punched at the near the folded edge. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Setup:
- Square paper folded horizontally from bottom to top
- Creates 2 overlapping layers
- Fold line is at the horizontal center

Step 2 - Fold Mechanics:
- Bottom half folds upward to cover top half
- Both layers are identical in size and shape
- Perfect alignment creates clean symmetry

Step 3 - Punch Location Analysis:
- Hole position: near the folded edge
- In folded state: appears close to the physical edge
- When unfolded: will appear near the center line

Step 4 - Unfolding Process:
- Carefully unfold along the horizontal crease
- Top layer hole remains at punch location
- Bottom layer hole mirrors across center line
- Result: Two holes close together near center horizontal line

Step 5 - Geometric Confirmation:
- Distance from center: equal for both holes
- Vertical alignment: both holes at same x-coordinate
- Pattern: symmetric about horizontal axis

Spatial Reasoning Technique:
Use coordinate geometry - if hole is at (x,y) on folded paper, unfolded positions are (x,y) and (x,100-y) for 100x100 paper.

Key Insight: The folded edge becomes the symmetry line when unfolded.

Question 14

A square sheet of paper is folded horizontal (top to bottom). A hole is punched at the center of folded paper. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Analysis:
- Starting with a square paper (transparent sheet)
- Performing a horizontal (top to bottom) fold
- This creates 2 layers of paper stacked vertically

Step 2 - Understanding the Fold:
- A horizontal fold creates a mirror line across the middle
- Any hole punched will appear on both layers
- The symmetry axis is horizontal, but hole alignment becomes vertical

Step 3 - Hole Punch Visualization:
- Hole location: center of folded paper
- When punched, it goes through both layers simultaneously
- Each layer will have the hole at the same relative position from the fold

Step 4 - Mental Unfolding:
- Unfold the paper back to original position
- The hole on the top layer stays in place (center)
- The hole on the bottom layer mirrors across the fold line
- Result: Two holes vertically aligned in the center

Step 5 - Verification:
- Check symmetry: Holes should be mirror images across horizontal center line
- Count: Single punch through 2 layers = 2 holes when unfolded
- Pattern matches: Two holes vertically aligned in the center

Mental Visualization Tip: Imagine tracing the fold line and reflecting the hole position across it like a mirror reflection.

Common Mistake to Avoid: Don't confuse horizontal and vertical fold patterns - horizontal folds create vertical symmetry in hole patterns.

Question 15

A square sheet of paper is folded horizontal (bottom to top). A hole is punched at the near the folded edge. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Setup:
- Square paper folded horizontally from bottom to top
- Creates 2 overlapping layers
- Fold line is at the horizontal center

Step 2 - Fold Mechanics:
- Bottom half folds upward to cover top half
- Both layers are identical in size and shape
- Perfect alignment creates clean symmetry

Step 3 - Punch Location Analysis:
- Hole position: near the folded edge
- In folded state: appears close to the physical edge
- When unfolded: will appear near the center line

Step 4 - Unfolding Process:
- Carefully unfold along the horizontal crease
- Top layer hole remains at punch location
- Bottom layer hole mirrors across center line
- Result: Two holes close together near center horizontal line

Step 5 - Geometric Confirmation:
- Distance from center: equal for both holes
- Vertical alignment: both holes at same x-coordinate
- Pattern: symmetric about horizontal axis

Spatial Reasoning Technique:
Use coordinate geometry - if hole is at (x,y) on folded paper, unfolded positions are (x,y) and (x,100-y) for 100x100 paper.

Key Insight: The folded edge becomes the symmetry line when unfolded.

Question 16

A square sheet of paper is folded horizontal (bottom to top). A hole is punched at the near the folded edge. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Setup:
- Square paper folded horizontally from bottom to top
- Creates 2 overlapping layers
- Fold line is at the horizontal center

Step 2 - Fold Mechanics:
- Bottom half folds upward to cover top half
- Both layers are identical in size and shape
- Perfect alignment creates clean symmetry

Step 3 - Punch Location Analysis:
- Hole position: near the folded edge
- In folded state: appears close to the physical edge
- When unfolded: will appear near the center line

Step 4 - Unfolding Process:
- Carefully unfold along the horizontal crease
- Top layer hole remains at punch location
- Bottom layer hole mirrors across center line
- Result: Two holes close together near center horizontal line

Step 5 - Geometric Confirmation:
- Distance from center: equal for both holes
- Vertical alignment: both holes at same x-coordinate
- Pattern: symmetric about horizontal axis

Spatial Reasoning Technique:
Use coordinate geometry - if hole is at (x,y) on folded paper, unfolded positions are (x,y) and (x,100-y) for 100x100 paper.

Key Insight: The folded edge becomes the symmetry line when unfolded.

Question 17

A square sheet of paper is folded horizontal (top to bottom). A hole is punched at the center of folded paper. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Analysis:
- Starting with a square paper (transparent sheet)
- Performing a horizontal (top to bottom) fold
- This creates 2 layers of paper stacked vertically

Step 2 - Understanding the Fold:
- A horizontal fold creates a mirror line across the middle
- Any hole punched will appear on both layers
- The symmetry axis is horizontal, but hole alignment becomes vertical

Step 3 - Hole Punch Visualization:
- Hole location: center of folded paper
- When punched, it goes through both layers simultaneously
- Each layer will have the hole at the same relative position from the fold

Step 4 - Mental Unfolding:
- Unfold the paper back to original position
- The hole on the top layer stays in place (center)
- The hole on the bottom layer mirrors across the fold line
- Result: Two holes vertically aligned in the center

Step 5 - Verification:
- Check symmetry: Holes should be mirror images across horizontal center line
- Count: Single punch through 2 layers = 2 holes when unfolded
- Pattern matches: Two holes vertically aligned in the center

Mental Visualization Tip: Imagine tracing the fold line and reflecting the hole position across it like a mirror reflection.

Common Mistake to Avoid: Don't confuse horizontal and vertical fold patterns - horizontal folds create vertical symmetry in hole patterns.

Question 18

A square sheet of paper is folded horizontal (bottom to top). A hole is punched at the near the folded edge. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Setup:
- Square paper folded horizontally from bottom to top
- Creates 2 overlapping layers
- Fold line is at the horizontal center

Step 2 - Fold Mechanics:
- Bottom half folds upward to cover top half
- Both layers are identical in size and shape
- Perfect alignment creates clean symmetry

Step 3 - Punch Location Analysis:
- Hole position: near the folded edge
- In folded state: appears close to the physical edge
- When unfolded: will appear near the center line

Step 4 - Unfolding Process:
- Carefully unfold along the horizontal crease
- Top layer hole remains at punch location
- Bottom layer hole mirrors across center line
- Result: Two holes close together near center horizontal line

Step 5 - Geometric Confirmation:
- Distance from center: equal for both holes
- Vertical alignment: both holes at same x-coordinate
- Pattern: symmetric about horizontal axis

Spatial Reasoning Technique:
Use coordinate geometry - if hole is at (x,y) on folded paper, unfolded positions are (x,y) and (x,100-y) for 100x100 paper.

Key Insight: The folded edge becomes the symmetry line when unfolded.

Question 19

A square sheet of paper is folded horizontal (bottom to top). A hole is punched at the near the folded edge. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Setup:
- Square paper folded horizontally from bottom to top
- Creates 2 overlapping layers
- Fold line is at the horizontal center

Step 2 - Fold Mechanics:
- Bottom half folds upward to cover top half
- Both layers are identical in size and shape
- Perfect alignment creates clean symmetry

Step 3 - Punch Location Analysis:
- Hole position: near the folded edge
- In folded state: appears close to the physical edge
- When unfolded: will appear near the center line

Step 4 - Unfolding Process:
- Carefully unfold along the horizontal crease
- Top layer hole remains at punch location
- Bottom layer hole mirrors across center line
- Result: Two holes close together near center horizontal line

Step 5 - Geometric Confirmation:
- Distance from center: equal for both holes
- Vertical alignment: both holes at same x-coordinate
- Pattern: symmetric about horizontal axis

Spatial Reasoning Technique:
Use coordinate geometry - if hole is at (x,y) on folded paper, unfolded positions are (x,y) and (x,100-y) for 100x100 paper.

Key Insight: The folded edge becomes the symmetry line when unfolded.

Question 20

A square sheet of paper is folded horizontal (top to bottom). A hole is punched at the center of folded paper. When unfolded, what pattern will appear?

Step-by-Step Solution:

Step 1 - Initial Analysis:
- Starting with a square paper (transparent sheet)
- Performing a horizontal (top to bottom) fold
- This creates 2 layers of paper stacked vertically

Step 2 - Understanding the Fold:
- A horizontal fold creates a mirror line across the middle
- Any hole punched will appear on both layers
- The symmetry axis is horizontal, but hole alignment becomes vertical

Step 3 - Hole Punch Visualization:
- Hole location: center of folded paper
- When punched, it goes through both layers simultaneously
- Each layer will have the hole at the same relative position from the fold

Step 4 - Mental Unfolding:
- Unfold the paper back to original position
- The hole on the top layer stays in place (center)
- The hole on the bottom layer mirrors across the fold line
- Result: Two holes vertically aligned in the center

Step 5 - Verification:
- Check symmetry: Holes should be mirror images across horizontal center line
- Count: Single punch through 2 layers = 2 holes when unfolded
- Pattern matches: Two holes vertically aligned in the center

Mental Visualization Tip: Imagine tracing the fold line and reflecting the hole position across it like a mirror reflection.

Common Mistake to Avoid: Don't confuse horizontal and vertical fold patterns - horizontal folds create vertical symmetry in hole patterns.
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