Credit card numbers follow certain patterns. A credit card must have between 13 and 16 digits. It must start with: â¢ 4 for Visa cards. â¢ 5 for Master cards. â¢ 37 for American Express cards. In 1954, Hans Luhn of IBM proposed an algorithm for validating credit card numbers. The algorithm is useful to determine if a card number is entered correctly or if a credit card is scanned correctly by a scanner.
The phrases used for discounted items include,  off, Save 50%, and Get a 20% discount.. Procedure: 1  To calculate the discount, multiply the rate by the original price. 2  To calculate the sale price, subtract the discount from original price.
Example of Preferred Stock Value Formula. An individual is considering investing in straight preferred stock that pays $20 per year in dividends. It has been determined that based on risk, the discount rate would be 5%. The price the individual would want to pay for this security would be $20 divided by .05(5%) which is calculated to be $400. The formula could be reworked to find the rate or return by dividing the fixed dividend payout by the price. For example, if the price is $40 per share and the annual dividend is $4, the rate would be .10 or 10%.