[jdwhit2]

  The tolerance - how far out one may be for the estimate to be accepted and the answer shown - must at all times appear reasonable ... The student should never feel that an estimate was unreasonably rejected, and on the other hand should not find an odd guess being accepted

The inventor had considered this question for 14 years while developing this calculator.

[ColinWright]

And now with linefeeds:

    The tolerance - how far out one may be for the estimate
    to be accepted and the answer shown - must at all times
    appear reasonable... The student should never feel that
    an estimate was unreasonably rejected, and on the other
    hand should not find an odd guess being accepted.

[sp332]

Or with automatic line breaks: The tolerance - how far out one may be for the estimate to be accepted and the answer shown - must at all times appear reasonable ... The student should never feel that an estimate was unreasonably rejected, and on the other hand should not find an odd guess being accepted.