It is sometimes assumed that the solution of a problem can be found to the same number of significant digits as the data. That this is not always so can be illustrated by the following example: the solution of the set of equations
123x ― 124y = 61, 248x―250y = 123
is x = 1, y = 0.5, while the solution of the perturbed set
123·01x ― 124y = 61, 248x ― 250y = 123
is x = ― 4, y = ―4·46!