The tailor had one bolt of grey wool, forty metres of it, and an order for coats. Each coat took six metres. The apprentice did the division in his head and said six coats.
"Six coats," the tailor agreed, "and four metres."
The boy had stopped at the whole number, the way people do. But in a workshop the remainder is not a leftover detail; it is cloth, and cloth is money. Four metres of grey wool would make two waistcoats, or the linings of three jackets, or nothing at all if it sat on the shelf until the moths found it.
"Every division has two answers," the tailor said. "How many, and what is left. If you ignore the second one you will run this shop for thirty years and never know where your money went."
He kept a ledger with a column for offcuts. At the end of a good year the column showed enough wool for eleven waistcoats, all of them made from cloth the apprentice would have called scrap.
There was one more lesson in it. When the order changed to coats of eight metres, the same bolt gave five coats and nothing at all left over. The tailor liked those orders least. A clean division looks tidy on paper, but it means the bolt has been used to the last centimetre and there is no margin if a sleeve is cut wrong.