11. In writing numbers between those in the above table, hundreds are written after thousands, tens after hundreds, and units after tens.

Thus, 1567 is written MDLXVII; 2053, MMLIII; 4508, IVDVIII; 3600, MMMDC.

NOTE 1. IIII = 4; XXXX

=

40; CCCC 400, are also in use.

NOTE 2. The use of the Roman system of notation is confined chiefly to the numbering of chapters and sections of books, pages of prefaces and introductions, medical prescriptions, public documents, divisions on clock dials, etc.

Exercise 3

Write by the Roman system the following:

1. The nine simple numbers.
3. The nine hundreds.

2. The nine tens.

4. The numbers between 10 and 30.
5. The numbers between 50 and 70.

6. The numbers between 80 and 100.

General Definitions

12. Quantity is anything that can be measured; as, weight, length, value, time.

13. A unit is any standard of reference employed in counting a collection or in measuring a quantity; as, a pound, a yard, a dollar, a day.

14. An amount is an expression denoting the number and kind of units in a quantity; as, 2 pounds, 5 yards, 6 dollars, 7 days.

15. Similar amounts are such amounts as are composed of the same kind of units; as, 3 bushels and 5 bushels.

16. Arithmetic is the science of numbers and the art of computing with them.

Reading and Writing Dollars and Cents

17. The sign & stands for dollar or dollars; c, ¢ or ct. stands for cent or cents.

Thus, 7 dollars may be written, $7; 5 cents may be written 5 c, 54, or 5 ct.

18. If a sum of money consists of dollars and cents, a point called the decimal point is written between the number of dollars and the number of cents. If the number of cents is less than ten, a cipher is written between the decimal point and the number of cents.

Thus, 4 dollars 65 cents is written $4.65, and 3 dollars 8 cents is written $3.08. 35 cents may be written $0.35.

FUNDAMENTAL PROCESSES

Addition

19. Addition is the process of uniting two or more numbers into one number called their sum.

NOTE. Similar amounts, and only such, may be united (added); the result (sum) is similar to the amounts added.

20. The sign of addition is +, read plus.

Thus, in Example 1, look for groups, as indicated, and say aloud:

10, 19, 28, 35.

Add at sight the following:

7. 54+37 Thus, say aloud: 54, 84, 91.

21. Find the sum of 372, 565, 356, and 489.

372

565

356

489

1782

Add from the bottom upward.

Add first the units, then the tens, then the hundreds.
What is the sum of the units?

The sum of the units is equal to how many tens and how many units over? How many tens are carried to the tens'

column from the sum of the units?

Counting in the number of tens carried, what is the sum of the tens? The sum of the tens is equal to how many hundreds and how many tens over? How many hundreds are carried to the hundreds' column from the sum of the tens? Counting in the number of hundreds carried, what is the sum of the hundreds? What is the sum of the numbers added?

See if the sum found agrees with the sum obtained when the columns are added downward.

22. Testing the correctness of a result by finding it in different ways or by using it in making comparisons is called checking the result.

(Accuracy and speed test.

Exercise 6

Practice until you can add each of the first 15 examples in this exercise and check the result in less than 2 minutes.)