1. Pay attention to the alignment of the numbers starting from the right.

2. After multiplication, count how many decimals there are in the factor, then count how many decimals there are on the right side of the product, and click on the decimal point.

A decimal that has an infinite number of digits in its decimal part and does not have one or several digits repeated in sequence is called an infinite non-repeating decimal, such as pi=3.14159265358979323, natural logarithm The base e=2.71828182845904. Infinite non-repeating decimals are irrational numbers and cannot be reduced to fractional form.

Finite decimal:

A decimal with a finite number of digits after the decimal part. For example, 3.1465, 0.364, 8.3218798456, etc., finite decimals are all rational numbers and can be converted into fractions.

A simplest fraction can be converted into a decimal finite decimal if and only if its denominator contains only prime factors 2 or 5 or both. Similarly, a simplest fraction can be transformed into a finite decimal of a positive integer base if and only if the prime factors of its denominator are a subset of the base prime factors.

Infinite decimals Starting from a certain digit of the decimal part, a number or several numbers, decimals that repeatedly appear in sequence are called recurring decimals. For example, 1/7=0.142857142857142857, 11/6=1.833333, etc. Repeating decimals are also rational numbers and can be converted into fractional form.