xie2010397
motorower
Dołączył: 07 Paź 2010
Posty: 251
Przeczytał: 0 tematów
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Skąd: England
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 Wysłany: Pon 7:30, 06 Gru 2010 Temat postu: Speed calculation, taught his son to keep the futu |
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1. ten by ten:
formulas: the head by head, tail plus tail, tail by tail.
Example: 12 × 14 =?
solution: 1 × 1 = 1
2 +4 = 6
2 × 4 = 8
12 × 14 = 168
Note: a bit multiply, not use the 0 digit placeholder.
2. head the same, complementary tail (tail add up to 10):
formulas: a first add 1 to the head by head, tail by tail.
Example: 23 × 27 =?
Solution: 2 +1 = 3
2 × 3 = 6
3 × 7 = 21
23 × 27 = 621
Note: a bit multiply,[link widoczny dla zalogowanych], not use the 0 digit placeholder.
3. complementary first multiplier,[link widoczny dla zalogowanych], the same as the other multiplier:
formulas: a first add 1 to the head by head,[link widoczny dla zalogowanych], tail by tail.
Example: 37 × 44 =?
solution: 3 +1 = 4
4 × 4 = 16
7 × 4 = 28
; 37 × 44 = 1628
Note: a bit multiply, not use the 0 digit placeholder.
4. dozens of dozens of one by one:
formulas: head by head,[link widoczny dla zalogowanych], head plus head, tail by tail.
Example: 21 × 41 =?
solutions: 2 × 4 = 8
2 +4 = 6
1 × 1 = 1
; 21 × 41 = 861
5.11 by any number:
formulas: sum of fixed fate, and the middle of the drop-down.
Example: 11 × 23125 =?
Solution: 2 +3 = 5
3 +1 = 4
1 +2 = 3
; 2 +5 = 7
2 and 5, respectively, in the sum of
11 × 23125 = 254375
Note: and over ten to get into one.
6. dozen by any number:
formulas: Second Take is not the first fate of several trends, the first digit multiplied by the factor behind the second factor of each number,[link widoczny dla zalogowanych], plus the next digit, again missing.
Example: 13 × 326 =?
solution: 13 bits is 3
3 × 3 +2 = 11
3 × 2 +6 = 12
; 3 × 6 = 18
13 × 326 = 4238
Note: and over ten to get into one.
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