[1] The name of the puzzle is associated with Mustonen's Survo system, which is a general environment for statistical computing and related areas.
Easy puzzles, meant for school children, are pure exercises in addition and subtraction, while more demanding ones require also good logic reasoning.
Survo puzzles have been published regularly in Finland by Ilta-Sanomat and the scientific magazine of the University of Helsinki from September 2006.
Solving of Survo puzzles was one of the three main topics in the national entrance examination of the Finnish universities in computer science (2009).
The solution is then easily completed as Thus basic arithmetics and simple reasoning is enough for solving easy Survo puzzles like this one.
[6] In their simplest form, as in the following 2 × 3 case (degree of difficulty 0) Survo puzzles are suitable exercises in addition and subtraction.
The problem can be simplified by giving some of the numbers readily, for example, as which makes the task almost trivial (degree of difficulty 0).
[6] Measuring the degree of difficulty is based on the number of 'mutations' needed by the first solver program made by Mustonen in April 2006.
This trial leads either to a correct solution or (as in most cases) to dead end where the discrepancy between computed and true sums cannot be diminished systematically.
In most cases, the mean number of mutations works as a crude measure for the level of difficulty of solving a Survo puzzle.
This measure (MD) is computed as the mean number of mutations when the puzzle is solved 1000 times by starting from a randomized table.
The degree of difficulty given as an MD value is rather inaccurate and it may be even misleading when the solution is found by clever deductions or by creative guesswork.
[10] The procedure is started by filling the original table by numbers 1,2,...,m·n according to sizes of these products and by computing row and column sums according to this initial setup.
[11] In this quick game, open 5 × 5 puzzles are solved by selecting (or guessing) the numbers by mouse clicks.