It may seem a matter of trivial importance whether the pupil increases the subtrahend number or decreases the minuend number when he subtracts digits that involve taking or borrowing; and yet investigation proves that to increase the subtrahend number is by far the simpler process, and eliminates both a source of waste and a source of error, which, in the aggregate, may assume a significance to mental economy that is well worth considering.
"Craftsmanship in Teaching"
William Chandler Bagley