Carbon paper trick with folding: three sheets and two carbons to get more copies A uses three sheets with two carbon papers to make two copies. Then he folds the set so the upper half lies over the lower half and types again. How many carbon copies (not counting the top original impression) does he now obtain?

Introduction / Context:
This puzzle relies on how carbon paper transfers impressions through layered sheets. Normally, with three sheets and two carbons you obtain two carbon copies beneath the top original. Folding the set cleverly allows the keystroke to produce duplicate transfers on the upper and lower halves, increasing the number of carbon copies.

Given Data / Assumptions:

• Initial stack (top to bottom): sheet, carbon, sheet, carbon, sheet.
• Typically yields 2 carbon copies under the top original.
• Stack is folded so the upper half overlays the lower half before typing.

Concept / Approach:
Folding aligns layers so each keystroke passes through two thicknesses of the set across the fold, creating duplicate contact sequences of sheet–carbon–sheet in both folded halves. Each such sequence yields a transferred copy, effectively doubling the number of carbon copies.

Step-by-Step Solution:

Verification / Alternative check:
Practical office folklore puzzle: the fold creates two parallel stacks during impact, each reproducing the normal two-copy path, giving four carbon copies (original still on the top sheet).

Why Other Options Are Wrong:

• 1, 2, 3: These ignore the doubling effect of the fold on the transfer paths.

Common Pitfalls:
Counting the original as a “copy” or assuming folding reduces transfer; in fact, it replicates it.

Final Answer:
4