secrets-of-mental-math-malestrom

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248 Answers 462 31 9. 431 2 184,800 31 2 185,761 31 400 32 1 31 2 960 1 2 961 1 30 800 19 10. 781 2 609,600 19 2 609,961 19 762 20 1 19 2 360 1 2 361 1 18 1,000 25 11. 975 2 950,000 25 2 950,625 25 950 30 5 25 2 600 5 2 625 5 20 Two-Digit Cubes (page 79) 1. 12 3 (10 12 14) (2 2 12) 1680 48 1728 2. 17 3 (14 17 20) (3 2 17) 4760 153 4913 3. 21 3 (20 21 22) (1 2 21) 9240 21 9261 4. 28 3 (26 28 30) (2 2 28) 21,840 112 21,952 5. 33 3 (30 33 36) (3 2 33) 35,640 297 35,937 6. 39 3 (38 39 40) (1 2 39) 59,280 39 59,319 7. 40 3 40 40 40 64,000 8. 44 3 (40 44 48) (4 2 44) 84,480 704 85,184 9. 52 3 (50 52 54) (2 2 52) 140,400 208 140,608 10. 56 3 (52 56 60) (4 2 56) 174,720 896 175,616 11. 65 3 (60 65 70) (5 2 65) 273,000 1,625 274,625 12. 71 3 (70 71 72) (1 2 71) 357,840 71 357,911 13. 78 3 (76 78 80) (2 2 78) 474,240 312 474,552 14. 85 3 (80 85 90) (5 2 85) 612,000 2,125 614,125 15. 87 3 (84 87 90) (3 2 87) 657,720 783 658,503 16. 99 3 (98 99 100) (1 2 99) 970,200 99 970,299
Answers 249 CHAPTER 4: DIVIDE AND CONQUER One-Digit Division (page 84) 1. 35 3 9 2. 145 1 5 3. 9318 5726 27 5 48 22 45 20 3 26 25 1 36 1 6 8289 24 49 48 1 4. 5. 442 2 3 6. 31328 12 12 08 6 2 Two-Digit Division (page 93) 1. 7 5 2. 3. 43 17 17738 68 58 51 7 4. 5. 6. 170 1 4 152 1 2 655 9 28 11 18 183074 18 127 126 14 284268 28 146 140 68 56 12 24 1 24 24591 48 111 96 15 117214 66 61 55 64 55 9 61 1 7 7428 42 08 7 1 695 2 4 42782 24 38 36 22 20 2 4 5 79 79321 316 5
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This book has been optimized for vi
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SECRE+S OF MEN+AL MA+H The Mathemag
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I dedicate this book to my wife, De
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Contents Foreword by Bill Nye (the
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Foreword by Bill Nye (the Science G
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Foreword xiii Well, actually, I hop
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Foreword xv there are also an infin
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xviii Foreword math nut. Immunizati
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xx Prologue in on his secrets of
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xxii Prologue where he learned thes
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xxiv Introduction Too often, math i
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2 Secrets of Mental Math 35 2 What
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4 Secrets of Mental Math Absolutely
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6 Secrets of Mental Math Similarly,
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8 Secrets of Mental Math Although I
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10 Secrets of Mental Math Exception
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12 Secrets of Mental Math math in y
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14 Secrets of Mental Math 67 28 8
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16 Secrets of Mental Math 858 7 re
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18 Secrets of Mental Math lot easie
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20 Secrets of Mental Math Carl Frie
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22 Secrets of Mental Math Of course
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24 Secrets of Mental Math 958 417
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26 Secrets of Mental Math to 10. We
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28 Secrets of Mental Math By roundi
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30 Secrets of Mental Math mentally,
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32 Secrets of Mental Math 48 40 8
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34 Secrets of Mental Math problems
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36 Secrets of Mental Math 3-BY-1 MU
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38 Secrets of Mental Math sometimes
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40 Secrets of Mental Math 376 (300
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44 Secrets of Mental Math BE THERE
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46 Secrets of Mental Math 41 2 1 42
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48 Secrets of Mental Math other squ
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50 Secrets of Mental Math WHY THESE
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52 Secrets of Mental Math Similarly
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54 Secrets of Mental Math Gardner o
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56 Secrets of Mental Math same digi
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New and Improved Products: Intermed
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60 Secrets of Mental Math 59 (60 1
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62 Secrets of Mental Math 88 (90 2
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64 Secrets of Mental Math To see ho
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66 Secrets of Mental Math Remember
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68 Secrets of Mental Math 67: 67 3
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70 Secrets of Mental Math EXERCISE:
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72 Secrets of Mental Math Rounding
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74 Secrets of Mental Math 2. The ea
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76 Secrets of Mental Math 13 1,000
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78 Secrets of Mental Math Chapter 8
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Chapter 4 Divide and Conquer: Menta
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82 Secrets of Mental Math Let’s t
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86 Secrets of Mental Math In using
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88 Secrets of Mental Math 682 23 I
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92 Secrets of Mental Math original
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94 Secrets of Mental Math way is to
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96 Secrets of Mental Math 6 7 8 .
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98 Secrets of Mental Math You can e
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100 Secrets of Mental Math A number
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102 Secrets of Mental Math Divisibi
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104 Secrets of Mental Math It is al
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106 Secrets of Mental Math So, To a
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Chapter 5 Good Enough: The Art of
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110 Secrets of Mental Math Notice t
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112 Secrets of Mental Math 8,367 5
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114 Secrets of Mental Math onds doe
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116 Secrets of Mental Math We obser
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118 Secrets of Mental Math Divide:
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120 Secrets of Mental Math roots. I
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122 Secrets of Mental Math MORE TIP
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124 Secrets of Mental Math I will s
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126 Secrets of Mental Math number o
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128 Secrets of Mental Math and sinc
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130 Secrets of Mental Math EXERCISE
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132 Secrets of Mental Math COLUMNS
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134 Secrets of Mental Math As illus
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136 Secrets of Mental Math 4. 3 5 8
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138 Secrets of Mental Math Next, we
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140 Secrets of Mental Math You have
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144 Secrets of Mental Math Step 4.
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146 Secrets of Mental Math Shakunta
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148 Secrets of Mental Math Here’s
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150 Secrets of Mental Math EXERCISE
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152 Secrets of Mental Math work by
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154 Secrets of Mental Math words: m
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156 Secrets of Mental Math 93: bum,
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158 Secrets of Mental Math And: 69
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162 Secrets of Mental Math 362 beco
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164 Secrets of Mental Math learned
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166 Secrets of Mental Math Once you
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168 Secrets of Mental Math Thomas F
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170 Secrets of Mental Math numbers
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172 Secrets of Mental Math Then do
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178 Secrets of Mental Math Using th
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180 Secrets of Mental Math Adding 8
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182 Secrets of Mental Math If both
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184 Secrets of Mental Math I diagra
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186 Secrets of Mental Math In our n
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188 Secrets of Mental Math produces
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190 Secrets of Mental Math be conve
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192 Secrets of Mental Math (e.g., 4
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194 Secrets of Mental Math As with
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196 Secrets of Mental Math I should
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Page 248 and 249: Chapter ∞ Epilogue: How Math Help
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Page 259 and 260: Answers CHAPTER 1: A LITTLE GIVE AN
Page 261 and 262: Answers 235 Three-Digit Subtraction
Page 263 and 264: 13. 757 14. 259 15. 297 297 16. or
Page 265 and 266: Answers 239 2 100 5. 98 2 9600 2 2
Page 267 and 268: Answers 241 2-by-2 Addition-Method
Page 269 and 270: 2-by-2 Factoring-Method Multiplicat
Page 271 and 272: Answers 245 13. 38 63 (9 7) 15.
Page 273: Answers 247 234 17 3. 217 2 46,800
Page 277 and 278: Answers 251 23. 4,425,575 No: 4 4
Page 279 and 280: Answers 253 7. 7 8 1 1 4 1
Page 281 and 282: Answers 255 9. 104,972 10. 5,462,74
Page 283 and 284: Square Root Guesstimation (page 150
Page 285 and 286: 3-by-2 Exercises Using Factoring, A
Page 287 and 288: 21. 281 or 281 (280 1) 44 (11 4
Page 289 and 290: Answers 263 3. 58,324 2 “Liver”
Page 291 and 292: 3-by-3 Multiplication (page 192) 1.
Page 293 and 294: Answers 267 13. 783 (87 9) 589 1
Page 295 and 296: Answers 269 5-by-5 Multiplication (
Page 297 and 298: Bibliography RAPID CALCULATION Cutl
Page 299 and 300: Index addition: an “amazing” su
Page 301 and 302: Index 275 factoring a number: in th
Page 303 and 304: Index 277 three-by-two problems, 16
Page 305: About the Authors DR. ARTHUR BENJAM
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