an numeral along number.
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,
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Example: 23 × 27 =?
Solution: 2 +1 = 3
2 × 3 = 6
3 × 7 = 21
23 × 27 = 621
Note: a bit amplify, no use the 0 digit placeholder .
3. complementary first multiplier, the same for the other multiplier:
formulas: a first add 1 to the head by head, 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, 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 medium 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: the whereabouts of the second activity is not the 1st multiplier, the first digit multiplied by the factor back the second factor of every number, and the next digit,
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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.
ashore double-digit multiplication in mathematics, The so-called 3, exactly equal to the sum of 10, I told him,
Minnetonka Moccasins Boots, multiplying the number favor this, in fact, there is a pattern. Two-digit number is the product of two digits for the post thanks to a number fewer than 10, ten digits with fill 0; both take the same number of one of the ten plus 1 multiplied,
Moccasins Shoes, the result is the thousands of Deshu bit and the hundred. Specific to the example above, 67 × 63,7 × 3 = 21, it is thanks to a number of 21 the last two; 6 × (6 +1) = 6 × 7 = 42, it is thanks to a number of the first two of 42 comprehensive up, 67 × 63 = 4221. Like, 15 × 15 = 225,89 × 81 = 7209,64 × 66 = 4224,92 × 98 = 9016. I told him this rapid calculation small In the I told him that the so-called is 5, the results of ten-digit just 4 +6 = 10. It's calculation rule is that the two of you the same number as the product of the number of digits later thanks to a number of less than 10, fill in the ten on 0; two-digit multiplication with dozens of the same digits, The result is that thanks to a number of one hundred and thousand digits. Specific to the above example, 45 × 65,5 × 5 = 25, it is thanks to a number of post 25 double-digit, 4 × 6 +5 = 29, it is thanks to a number of the front part 29, therefore, 45 × 65 = 2925. Like, 11 × 91 = 1001,83 × 23 = 1909,74 × 34 = 2516,97 × 17 = 1649.
for ease of us apt comprehend the universal statute of double-digit multiplication, there ambition be through specific samples. By comparing the results of a colossal number of double-digit multiplication, I double-digit multiplication outcome namely divided into 3 chapters, a bit, ten, ten alternatively more that one hundred and thousands. (Maximum two-digit multiplication is not more than 10,000,
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which, thanks to a number of digits is determined, taking the number two product of the mantissa digit for the Deshu the unattached digits. Specific to the example above, 2 × 6 = 12, where 2 is thanks to a number of mantissa, 1 bit into the digit;
thanks to a number of ten digits is determined, taking the number of bits of two and ten,
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Deshu the rest of the method is insistent, catching the number 2 the product of ten and ten-digit binary number and is thanks to a number of one hundred or a thousand. Specific to the example above, 4 × 5 +3 = 23. The 2 and 3, respectively thanks to a number of the thousands digit and the hundreds.
Therefore, 42 × 56 = 2352. Another example, 82 × 97, in accordance with the on measurement method, first identified thanks to a number of digits, 2 × 7 = 14, then thanks to a number of bits ought be 4; then determined thanks to a number of ten-digit, 2 × 9 +8 × 7 +1 = 75, then thanks to a number of ten median 5; final reckoned the rest of Deshu, 8 × 9 +7 = 79, accordingly, 82 × 97 = 7954. Similarly, using this algorithm, it is cozy to penetrate that always the production of two-digit multiplication.
Quick enumeration usage ( add )
Linear Mode
