Multiply two numbers with the same head and complementary tail. Multiply two digits with the same complementary head and tail, and multiply any two real numbers.

Ten digits are the same, and the sum of single digits is equal to the multiplication of two digits of 10. The expression is ab*a( 10-b), where ab stands for ten digits and one digit respectively. The result is that the number of thousands and hundreds is a*(a+ 1), and the number of tens is b*( 10-b), as listed in 37*33= 122 1.

Five-digit square algorithm, the expression is a5*a5, and A stands for the number before 5. The result is that the product of ten digits and 25 and the previous number is a*(a+ 1), for example, 55*55=3025.

Extended data:

Precautions for users to calculate quickly:

It is necessary to do more topic training. As the saying goes, practice makes perfect. Do more questions. When you meet a brain that can calculate quickly, you will quickly search for the corresponding formula.

Reciting formulas is also skillful. We should classify memories and find out the similarities. We can't just memorize multiplication formulas like now, and we don't need to understand them, but the formulas of area, volume and perimeter of various figures can't be memorized. We need to understand memory, so that we can remember it firmly.

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