CAFUFA
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Multiples of 7
Multiples of 7 are the results of 7 times a whole number: 0, 7, 14, 21, 28 and so on, forever. Dividing a multiple of 7 by 7 leaves no remainder.
Multiples of 7 up to 100
There are 14: 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91, 98. (0 is also a multiple of 7, and of every number.)
List of multiples of 7 up to 700
- 7
- 14
- 21
- 28
- 35
- 42
- 49
- 56
- 63
- 70
- 77
- 84
- 91
- 98
- 105
- 112
- 119
- 126
- 133
- 140
- 147
- 154
- 161
- 168
- 175
- 182
- 189
- 196
- 203
- 210
- 217
- 224
- 231
- 238
- 245
- 252
- 259
- 266
- 273
- 280
- 287
- 294
- 301
- 308
- 315
- 322
- 329
- 336
- 343
- 350
- 357
- 364
- 371
- 378
- 385
- 392
- 399
- 406
- 413
- 420
- 427
- 434
- 441
- 448
- 455
- 462
- 469
- 476
- 483
- 490
- 497
- 504
- 511
- 518
- 525
- 532
- 539
- 546
- 553
- 560
- 567
- 574
- 581
- 588
- 595
- 602
- 609
- 616
- 623
- 630
- 637
- 644
- 651
- 658
- 665
- 672
- 679
- 686
- 693
- 700
How to tell if a number is divisible by 7
For 2, 5 and 10 you just look at the last digit. There's no shortcut that quick for 7, but there is a rule:
- Take off the last digit of the number.
- Double that digit.
- Subtract it from what's left.
- If the result is a multiple of 7 (or 0), so is the original number. If it's still big, repeat.
Examples:
- 343: 34 − 2 × 3 = 28. Since 28 is a multiple of 7, so is 343 (343 = 7 × 49).
- 686: 68 − 2 × 6 = 56. It's a multiple (686 = 7 × 98).
- 1001: 100 − 2 × 1 = 98, and 98 = 7 × 14. It's a multiple (1001 = 7 × 143).
- 100: 10 − 2 × 0 = 10. Not a multiple of 7.
Multiple of 7 or ending in 7: the Cafufa rule
In Cafufa, numbers come up in order and you hit CAFUFA on every multiple of 7 and every number ending in 7. From 1 to 100 that's 22 numbers, marked in yellow:
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 100
Watch out for the traps: 71 to 76 are neither multiples of 7 nor end in 7. And 57 and 87 end in 7 without being multiples (57 = 3 × 19 and 87 = 3 × 29).
How far can you get before a mistake? Free, no sign-up.
See also
The 7 times table with tricks to remember it, the Buzz counting game, and the numbers that knock out the most Cafufa players.