Quantity and Numbers in Algebra
"Whatever may be regarded as being made up of parts like the whole is called a Quantity.
To measure a quantity of any kind is to find how many times it contains another known quantity of the same kind.
A known quantity which is adopted as a standard for measuring quantities of the same kind is called a Unit. Thus, the foot, the pound, the dollar, the day, is units for measuring distance, weight, money, time.
A Number arises from the repetitions of the unit of measure, and shows how many times the unit is contained in the quantity measured.
When a quantity is measured, the result obtained is expressed by prefixing to the name of the unit the number which shows how many times the unit is contained in the quantity measured ; and the two combined denote a quantity expressed in units. Thus, 7 feet, 8 pounds, 9 dollars, 10 days, are quantities expressed in their respective units.
When a question about a quantity includes the unit, the answer is number; when it does not include the unit, the answer is a quantity. Thus, if a man who has fifteen bushels of wheat be asked how many bushels of wheat he has, the answer is the number fifteen ; if he be asked how wheat he has, the answer is the quantity, fifteen bushels.
A number answers the question, How many? a quantity, the question, How much ?