This is an aptitude question which looked simpler to me than it actually is and got me stuck. The question asks:     What is the maximum number of cylindrical pencils of $0.5$ cm diameter that can be stood in a square shaped stand of $5$ cm $\times$ $5$ cm cross-section?   I am aware of hexagonal packing but i really don't know how to get the answer which says it should be $105$ pencils.  EDIT  A link to this question already asked  found later.
I am working on the following problem asked in an examination: "What is the maximum number of cylindrical pencils of 0.5 cm diameter that can be stood in a square shaped stand of 5cm × 5cm inner cross section? 1. 99    2. 121   3. 100    4. 105." A simple calculation yielded me the answer 100.  But the answer in the key is 105. I don't how such an answer is possible. Any hint please.....Thanks in advance!
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