In March, a shop selling kitchen appliances in Bukhara raised the price by 20 percent on its best-selling kettle. The kettle had cost 50 dollars, so the new price was 60.
Sales fell sharply. In May, the owner, Kamola, decided to undo the change and told her assistant to cut the price by 20 percent. The assistant changed the price tag to 48 dollars.
A regular customer noticed at once. "In February this kettle cost 50," he said. "You raised it by twenty percent and lowered it by twenty percent. Why is it 48?"
Kamola explained that the two percentages were taken from different numbers. The increase was 20 percent of 50, which is 10 dollars. The decrease was 20 percent of 60, which is 12 dollars. The second change was larger because it started from a larger price.
She worked out what percent of the original price the kettle now cost: 48 out of 50, or 96 percent. To return to exactly 50 dollars, the price should have been reduced by 10 dollars, which is only about 16.7 percent of 60.
The customer bought the kettle at 48, pleased to have saved two dollars on a pricing mistake. Kamola changed her rule the same day: every price change in the shop is now written as a new price, not as a percentage.