One, the unit is the square of two digits of 5, the product is the multiplication of the unit at the end, the ten digits are multiplied by a larger number 1, and the product is put in the first place. For example,
25×25=625
Second, a two-digit number multiplied by 1 1 is obtained.
The product is, pull on both sides and add in the middle.
For example, 34× 1 1 = 374.