Jasur owns a small stationery shop. In his ledger he writes each day's profit in black ink and each day's loss in red, just as his father did.
The first week of the school holidays was difficult. Monday showed a loss of 40 dollars after a delivery of notebooks arrived damaged. Tuesday brought a small profit of 25 dollars. On Wednesday the shop lost another 15 dollars, because Jasur paid for a broken window. On Thursday a school ordered pens for its new teachers, and the shop made 60 dollars.
On Friday evening his daughter asked how the week had gone. "Two red days and two black days," Jasur said. "So we broke even?"
She added the black numbers first, 25 and 60, which made 85. Then the red numbers, 40 and 15, which made 55. The difference was 30 dollars in black. "Not even," she said. "We are 30 dollars ahead."
Jasur had counted the days instead of the money. Two losses and two gains say nothing about the net result; only the amounts do. A single large gain can cover several small losses, and a single large loss can wipe out a good week.
From then on, Jasur wrote the weekly total at the bottom of every page, in black or red, so the number would speak for itself.