Speed Mathematics

Quick and Easy Math

To copyreaders everywhere

who deserve so much credit

and get so little

FOURTH PRINTING

COPYRIGHT

C

© 1964 BY lSAAC ASIMOV

ALL lUGHTS lIESERVEO INCLUDlNG THE IUGHT TO l\El'RODUCE

'!HIS JIOOI:: OIl PARTs 'tHEREOF IN ANY FORM

LIBRARy OF CONGRESS CATALOG CAIro NlJMlIJ::R:

;PRINTED IN THE U.

~

s. A.

64-12216

CONTENTS

1

Why Shortcuts?

1

2

Addition

7

Naming the Parts of Addition

Carrying

Adding Left to Right

Round Numbers

Checking Addition

5

35

35

41

Multiplication

45

The Multiplication Table

Beyond the Multiplication Table

Making the Multiplier a Sum

Doubling

Checking Multiplication

4

Subtraction

Addition in Reverse

Checking Subtraction

3

26

45

Division

71

The Perils of DiviSion

Divisibility by 2,5, and 10

Divisibility by 4 and 8

Divisibility by 3, 6, and 9

Other Divisibilities

The Division Table

Rewriting Divisions

Long Division

Checking Division

71

7

10

14

22

50

55

62

67

75

78

84

88

94

98

102

109

7

Decimals

112

Zeros in Reserve

Freeing the Decimal Point

Manipulating Decimals

Simplifying by DecimGl

DoU(lrs and Cents

Percentage

Checking the Decimal Point

The Uses of Approximation

6

112

118

122

132

139

142

147

153

Fractions

159

Manipulating Fractions

Fractions and Decimals

M ultipliootion of Fractions

Fractions and Percentage

Changing Fractions into Whole NurniJers

159

163

168

174

177

Index

181

Author's Note

THIS BOOIC describes methods for solving arithmetical problems by "quick and easy" routes. These are not intended

to replace the more systematic methods familiar to everyone but to supplement them.

It is customary in books such as this to include many

exercises to develop the reader's confidence and skill in

handling these easy but possibly new techniques. However,

such exercises would clutter the book and reduce the room

available for...