It is often the case in which it is necessary to determine the mean weighted of a certain number of items: this type of average can be used to find, for example, the average cost of shares purchased at different times and at different prices, or to determine, during the inventory phase, the average price of an item purchased at different prices. This program computes quickly the weighted average of a series of quantities. We must introduce the data that refer to the unit value and the number of units for each item.