Brain Teasers
Nail the Square
A 27" x 27" square metal plate needs to be fixed by a carpenter on to a wooden board. The carpenter uses nails all along the edges of the square such that there are 28 nails on each side of the square. Each nail is at the same distance from the neighboring nails. How many nails does the carpenter use?
Answer
The four corners of the square have one nail each.Each side of the square now requires 26 nails (excluding the four corners).
Thus, Total number of nails used = 4 + (4 x 26) = 108.
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Comments
Or if you want to think of it as 4 lines holding 27 nails each, that fit perpindicular to eachother to create a square. It was easier for me.
I got the answer even though the teaser wording does not require that there are nails on the corner. The last nail along each side could be positioned such that the diagonal to the neighboring nail on the adjacent side was the same distance as the spacing between nails along the side.
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