secrets-of-mental-math-malestrom

278
Index
simplification, 13
division, 82, 90–93, 98
fractions, 96–97, 103–4;
exercises, 104; answers, 252
square roots, 211–12
Skeptics Society, 222
Smith, Steven, xxi
Sphinx, construction of, 229
square roots:
of four-digit numbers, 119
guesstimation, 117–21;
exercises, 130; answers, 255
with pencil and paper, 135–38;
exercises, 150; answers, 257
simplified, 211–12
of six-digit numbers, 119–20
of three-digit numbers, 119
of two-digit numbers, 119
squaring, 4–8
five-digit numbers, 177–80;
exercises, 180; answers,
262–64
four-digit numbers, 164–69;
exercises, 169; answers, 258
numbers that end in 5, 4–5,
47–48
rounding down in, 72
rounding up in, 71
three-digit numbers, 71–76;
exercises, 76; answers, 246–48
three-digit numbers using
mnemonics, 158–61
two-digit numbers, 44–48;
exercises, 48; answers, 238–40
why these tricks work, 51–52
subtraction:
borrowing in, 22–23, 24
complements, 25–28
fractions, 106–7; exercises, 107;
answers, 252–53
guesstimation, 111–12;
exercises, 129; answers, 254
left to right, 6–7, 21–28
in multiplying three-by-three
numbers, 190–91; exercises,
192–93; answers, 265–68
in multiplying three-by-two
numbers, 173–75; exercises,
175–76; answers, 259–62
in multiplying two-digit
numbers, 59–63; exercises, 63;
answers, 242
no borrowing in, 22, 23–24
with paper and pencil, 134–35;
exercises, 150; answers,
256
three-digit numbers, 23–25;
exercises, 28; answers,
235
two-digit numbers, 21–23;
exercises, 23; answers, 234
Sulloway, Frank J., 227
supermarket, guesstimation of total
charge, 111; exercise, 128;
answer, 253
tarot-card readings, 224
1089 magic, 200–202
tips (restaurant), calculating, 8,
122–23; exercises, 130;
answers, 256
UFO sightings, 230
when-all-else-fails method,
191–92