Memorising key square roots and using mental math tricks saves time. Techniques like the nearby perfect square trick and weighted averaging enhance problem-solving skills.

Square root days happen only a few times in a century, and the man who brought the day fame is celebrating his sixth one.

Memorising key square roots and using mental math tricks saves time. Techniques like the nearby perfect square trick and weighted averaging enhance problem-solving skills.

A version of this article appears in print on Nov. 23, 2010, Section D, Page 4 of the New York edition with the headline: An Exhibition That Gets to the (Square) Root of Sumerian Math.

This May marks the only time a calendar has a Square Root Day in a 20-year span, with the last one being on April 4, 2016.