Stores buy items from a wholesaler or distributer and increase the price when they
sell the items to consumers. The increase in price provides money for the operation
of the store and the salaries of people who work in the store.
A store may have a rule that the price of a certain type of item needs to be
increased by a certain percentage to determine how much to sell it for. This
percentage is called the markup.
If the cost is known and the percentage markup is known, the sale price is
the original cost plus the amount of markup. For example, if the original cost
is $4.00 and the markup is 25%, the sales price should be $4.00 + $4.00*25/100 = $5.00.
A faster way to calculate the sale price is to make the original cost equal to
100%. The markup is 25% so the sales price is 125% of the original cost. In the
example, $4.00 * 125/100 = $5.00.