or Truck, is the exchanging of one commodity for another. The word comes from the Spanish baratar, to deceive or circumvent in bargaining, perhaps because those who deal this way usually endeavour to overreach one another. To transact properly, the price of one of the commodities, and an equivalent quantity of the other, must be found either by practice or by the rule of three. The value or price of the goods received and delivered in barter being always equal, it is obvious that the product of the quantities received and delivered, multiplied into their respective rates, will be equal. Hence arises a rule which may be used with advantage in working several questions; namely, multiply the given quantity and rate of the one commodity, and the product, divided by the rate of the other commodity, quotes the quantity sought, or, divided by the quantity, quotes the rate.