A square paper is folded in half vertically (right edge over left edge), then in half horizontally (bottom edge over top edge), and then in half vertically again (right edge over left edge). This forms a smaller rectangle.
Three punches are made on this folded rectangle:
- Punch 1: Exactly at the bottom-right corner (where all folded edges meet).
- Punch 2: Exactly at the midpoint of the bottom edge.
- Punch 3: Strictly in the interior of the rectangle, not touching any edge.
How many distinct holes will be present when the paper is completely unfolded?
B
Step-by-Step Solution
Key idea: This is a reverse-engineering question testing layer counting and the effect of fold lines on punch holes. The number of distinct holes depends on how many fold lines the punch intersects.
Step 1: Trace the folds. Fold 1 (vertical) creates a fold line. Fold 2 (horizontal) creates a fold line. Fold 3 (vertical) creates another fold line. The paper has 8 layers.
Step 2: Identify the edges of the final rectangle. The bottom-right corner is the intersection of the folded edges. It corresponds to the center of the original square and lies on ALL THREE fold lines.
Step 3: Analyze Punch 1. It is at the bottom-right corner. Since it lies on all 3 fold lines, unfolding it merges all 8 layers into a single hole at the center of the original square. (1 hole)
Step 4: Analyze Punch 2. It is at the midpoint of the bottom edge. The bottom edge corresponds to the horizontal fold line only. It does not lie on the vertical fold lines. Thus, it lies on exactly 1 fold line. Unfolding across this fold line merges 2 layers, and the other 2 folds reflect this single hole to 4 locations. (4 holes)
Step 5: Analyze Punch 3. It is strictly in the interior, lying on 0 fold lines. It pierces 8 layers, and unfolding yields 8 distinct holes. (8 holes)
Step 6: Total holes = 1 + 4 + 8 = 13.
Answer: (B)