our hands without dividing, we can add automatically. If the units column adds up to 21, we put down I and carry 2; if it bad added up to 57, we would have put down 7 and carried 5, and so on.
The only reason this works, mind you, is that in adding a set of figures, each column of dicits (starting from the right and working leftward) represents a value ten times as great as the column before. The rightmost column is units, the one to its left is tens, the one to its left is hun dreds, and so on.
It is this combination of a number system based on ten and a value ratio from column to column of ten that makes addition very simple. It is for this reason that it is, as Pike calls it, "simple addition."
Now suppose you have I dozen and 8 apples, your friend has 1 dozen and 10 apples, and a passing stranger has I dozen and 9 apples. Make a pile of those and add them as follows:
I dozen 8 units
1 dozen 10 units
1 dozen 9 units
Since 8 + 10 + 9 = 27, do we put down 7 and carry 2? Not at all! The ratio of the "dozens" column to the (tunits" column is not 10 but 12, since there are 12 units to a dozen. And since the number system we are using is based on I 0 and not on 12, we can no longer let the dicits do our thinking for us. We have to go long way round.
If 8 + 10 + 9 - 27, we must divide that sum by the ratio of the value of the columns; in this case, 12. We find that 27 divided by 12 gives a quotient of 2 plus a remain der of 3, so we put down 3 and carry 2. In the dozens column we get I + I + 1 + 2 = 5. Our total therefore is 5 dozen and 3 apples.
Whenever a ratio of other than 10 is used so that you have to make actual divisions in adding, you have "com pound addition." You must indulge in compound addition if you try to add 5 pounds 12 ounces and 6 pounds 8 ounces, for there are 16 ounces to a pound. You are stuck again if you add 3 yards 2 feet 6 inches to I yard 2 feet 8 inches, for there are 12 inches to a foot, and 3 feet to a yard.
You do the former if you care to; I'll do the latter.
First, 6 inches and 8 inches are 14 inches. Divide 14 by 12, getting 1 and a remainder of 2, so you put down 2 and carry 1. As for the feet, 2 + 2 + I = 5. Divide 5 by 3 and get I and a remainder of 2, put down 2 and carry 1. In the yards, you have 3 + 1 + 1 = 5. Your answer, then, is 5 yards 2 feet 2 inches.
Now why on Earth should our unitratios vary all over the lot, when our number system is so firmly based on 10?
There are many reasons (valid in their time) for the use of odd ratios like 2, 3, 4, 8, 12, 16, and 20, but surely we are now advanced and sophisticated enough to use 10 as the exclusive (or n arly exclusive) ratio. If we could do so, we could with such pleasure forget about compound addition-and compound subtraction, compound multipli cation, compound division, too. (They also exist, of course.)
To be sure, there are times when nature makes the uni versal ten impossible. In measuring time, the day and the year have their lengths fixed for us by astronomical condi tions and neither unit of time can be abandoned. Com pound addition and the rest will have to be retained for suchspecial cases, alas.
But who in blazes says we must measure things in firkins and pottles and Flemish ells? These are purely man made measurements, and we must remember that measures were made for man and not man for measures.
It so happens that there is a system of measurement based exclusively on ten in this world. It is called the metric system and it is used all over the civilized world except for certain English-speaking nations such as the United States and Great Britain.
By not adopting the metric system, we waste our time for we gain. nothing, not one