Adopt the method of "top ten combination" for training. The method of "combining the first ten digits with the last ten digits" is two digits, their ten digits are the same, and the sum of the single digits is 10.

Multiply the two digits of "Top Ten and Last Ten", the two digits on the right of the product are just the product of single digits, and the number on the left of the product is just the product of the number on the tenth digit multiplied by 1 larger than it, and the combination is their product. For example, 54×56=3024,

8 1×89=7209。

Pay attention to "combination of left and right numbers"

The fast algorithm of multiplying any two digits by 99 or any three digits by 999 is called "left and right two-digit array method".