THE

YOUTH'S ASSISTANT

IN

THEORHETIC AND PRACTICAL

ARITHMETIC;

DESIGNED FOR THE USE OF

SCHOOLS IN THE UNITED STATES.

BY ZADOCK THOMPSON, A. M,
Author of the Gazetteer of the State of Vermont.

SIXTH EDITION.

Burlington:

EDWARD SMITH.

1832.

The following explanations and table, not being contained in the Written Arithmetic, are inserted here for the convenience of those who have not studied the Mental Arithmetic.

=EQUALITY is expressed by two horizontal marks; thus 100 cts.= 1 dollar, signifies that 100 cents are equal to one dollar. +ADDITION is denoted by a cross, formed by one horizontal and one perpendicular line, placed between the number; as 4+5=9, signifying that 4 added to 5 equals 9.

X MULTIPLICATION is denoted by a cross, formed by two oblique lines placed between the numbers; as 5 x 3=15, signifying that 5 multiplied by 3, or 3 times 5 are equal to 15.

-SUBTRACTION is denoted by one horizontal mark, placed between the numbers; as 7—4—3, signifying that 4 taken from 7 leave 3. (or DIVISION is denoted three different ways; 1st. by the reversed parenthesis; 2dly. by a horizontal line placed between the numbers with a dot on each side of it; and 3dly. by writing the number to be divided over the other in the form of a fraction; thus 2)6(3, and 6÷2-3 and 3, all signify the same thing, namely that if 6 be divided by 2 the quotient is 3.

MULTIPLICATION AND DIVISION TABLE.

1 2

2

34

5 6 7 8

9 10

11

12

4 6 8 10 12 14 16 3 6 9 12 15 18 | 21 | 24 4 812 16 20|24|28|32 510 15 20 25 30 | 35 | 40 6|12|18|24| 30 | 36 | 42 | 48 7|14|21| 28 | 35 | 42 | 49 | 56 8162432 | 40 | 48 | 56 | 64 91182736 | 45 | 54 | 63 | 72 10 20 30 40 | 50 | 60 | 70 | 80 1122 | 33 | 44 | 55 66 77 88

T

81 90 99 108
90 100 110 120

99 110 121 | 132

12|24|36|48|60| 72 |84|96| 108 | 120 | 132 | 144

Entered according to Act of Congress, in the year one thousand eight hundred and twenty eight,' by ZADOCK THOMPSON, in the Clerk's Office of the District of Vermont.

GEORGE AND VON PLIMPTON
JANUARY 29, 1924

(To the fourth edition. )

WHEN the improved edition of this work was published, in 1828, it was intended that the Written Arithmetic, which forms the second and third parts should always be accompanied by the Mental Arithmetic embraced in the first part. Since that time it has, however, been thought best to transpose such tables from the Mental to the Written Arithmetic, as to render the latter complete without the former, in order to lessen the expense of the book to those who do not wish to study mental arithmetic, or who have studied some other treatise; and, thus prepared, it is now presented to the public. No alteration has been made from the last edition in the arrangement of the rules, and the whole of the second part is presented, as before, on the inductive plan of Lacroix. The principles are first developed by the analysis of familiar examples, and the method of applying these principles to the solution of questions is then expressed in general terms, forming a Rule, which is still further illustrated by a great variety of practical questions. The analysis is printed in small type, occupies but little space, and may be omittedby those who wish to use rules without understanding them.

Addition and Multiplication, both involving the same principles, are presented in connexion, and also Subtraction and Division. A knowledge of decimals being necessary to a good understanding of our Federal currency and this knowledge being easily acquired by such as have learned the notation of whole numbers, decimals and Federal money are introduced immediately after the first section on simple numbers. By acquainting the pupil thus early with dicimals, he will be likely to understand them better and to avail himself of the facilities they afford in the solution of questions and the transaction of business.

Reduction ascending and descending are arranged in parallel columns and the answers to the questions of one column are found in the corresponding questions of the other. Compound multiplication and division are arranged in the same way, and only one general rule for each is given, which was thought better than to perplex the pupil with a multiplicity of cases.

Interest and other calculations by the hundred are all treated decimally, that method being most simple and conformable to the notation of our currency. The nature and principles of proportion are fully developed and the method of applying them to the solution of questions clearly shown.

The written arithmetic of fractions being, to young pupils, some. what difficult to be understood, is deferred till they are made famlliar with the most important arithmetical operations performed with whole numbers and decimals. The nature of roots and powers has been more fully explained in the present edition, and several new diagrams introduced for their elucidation. Throughout the

second part, it has been our main object to familiarize the pupil
with the fundamental principles of the science, believing that
when these are well understood, he will find no difficulty in applying
them to the particular cases which may occur.

The third part is mostly practical, and composed of such rules
and other matters as we conceived would be interesting and useful
to the student and the man of business.

PART II.

WRITTEN ARITHMETIC.

SECTION I.

NOTATION AND NUMERATION.

70. An individual thing taken as a standard of compari son, is called unity, a unit, or one.

71. Number is a collection of units, or ones.

72. Numbers are formed in the following manner; one and one more are called two, two and one, three, three and one, four, four and one, five, five and one, six, six and one, seven, seven and one, eight, eight and one, nine, nine and one, ten; and in this way we might go on to any extent, forming collections of units by the continual addition of one, and giving to each collection a different name. But it is evident, that, if this course were pursued, the names would soon become so numerous that it would be utterly impossible to remember them. Hence has arisen a method of combining a very few names, so as to give an almost infinite variety of distinct expressions. These names, with a few exceptions, are derived from the names of the nine first numbers, and from the names given to the collections of ten, a hundred, and a thousand units. The nine first numbers, whose names are given above, are called units, to distinguish them from the collections of tens, hundreds, &c. The collections of tens are named ten, twenty, thirty, forty, fifty, sixty, seventy, eighty, ninety.(6). The intermediate numbers are expressed by joining the names of the units with the names of the tens. To express one ten and four units, we say fourteen, to express two tens and five units, we say twenty-five, and others in like manner. The collections of ten tens, or hundreds, are expressed by placing before them the names of the units; as, one hundred, two hundred, and so on to nine hundred. The intermediate numbers are formed by joining to the hundreds the collections of tens and units. To express two hundred, four tens, and six units, we should