Multiply the same number with the remainder.

Simple calculation condition

Multiply two digits.

Same number: a multiplier has the same beginning and end; Complement: The sum of the first and last digits of another number is 10.

For example:

Judging that 44×3744 is the same number; 37 is the remainder: 3+7= 10 satisfies the simplification condition.

Simplified calculation method

The prefix of 1. complement is added with 1, the prefix is multiplied by the prefix written in front, and the mantissa is multiplied by the mantissa written in the back, that is, quadrature.

2. For example:

(3+ 1)×4= 16 is the product of thousands and hundreds; 4×7=28 is one tenth of the product and the unit;

So 44×37= 1628

3. Special attention: When the product of two mantissas is less than 10, a 0 must be added before the product.

For example: 55×9 1

A judgment: 55 is the same number, 9 1 satisfies 9+ 1= 10 is the remainder, and the simplification condition is satisfied.

B operation: (9+ 1)×5=50 is written on the thousands and hundreds of the product; 5× 1=5, and the pre-complement of 0 into 05 is written in the ten digits and one digit of the product, so 55×9 1=5005.