The basic method is trial quotient, which is determined by divisor × quotient closest to dividend.

If 5÷2 can be quotient 1 or quotient 2, but the divisor 2× quotient 2=4 is closest to 5, it is determined that quotient 2 is written as 5 ÷ 2 = 2... 1, where 1 is called the remainder. You can also continue to divide by the remainder 1, 1÷2, and then the decimal point becomes 2 after quotient 2. Then add 0 after the remainder 1 to become 10 to get the quotient 5 of 10, so the whole quotient becomes 2.5. Finish writing 5÷2=2.5

That's it.

To multiply, use the multiplication formula, and then add the number to the radix.

For example,12× 2 = 2× 2+2×10 = 4+20 = 24, where the top ten 2× 1=2 is written on the left side of the unit number 4, which is called carry-2×10 = in the horizontal direction. The vertical type is represented by 2× 1=2, which is shifted to the left by one bit, and 4 bits are added to the right of 2 to get 24.