1, first quadrature according to the law of integer multiplication;

2. See how many decimal places the multiplicand and multiplier * * * have, and count the decimal places from the right side of the product.

3. If there is a 0 after the decimal point, cross out the 0 after the decimal point according to the basic properties of the decimal point.

For example, 6.49×7.5=48.675, and its calculation steps are shown in the following figure:

Extended data:

The new meaning of multiplication: multiplication is not a simple symbol of addition.

Multiplication principle: If the dependent variable f is in direct proportion to the independent variable X 1, X2, X3...Xn, and each independent variable is qualitatively different, if any independent variable f is missing, it will lose its meaning, which is called multiplication.

In probability theory, the result of an event needs to be divided into n steps, the first step 1 includes M 1 different results, the second step includes M2 different results, …, and the n step includes Mn different results. Then this event may have n = m 1× m2× m3×…× Mn different results.

The multiplication of integers meets the following requirements: commutative law, associative law,? Law of distribution, law of elimination.

With the development of mathematics, the object of operation has developed from integer to more general group.

Intra-group multiplication is no longer needed to satisfy the commutative law. The most famous noncommutative example is the quaternion group discovered by Hamilton. But the law of association is still satisfied.

1. Multiplication commutative law:, Note: letters are multiplied by letters, and the multiplication sign need not be written, but can also be written.

2. Multiplicative associative law:.

3. Law of multiplication and distribution:

A decimal with a finite number of digits after the decimal part. For example, 3. 1465, 0.364, 8.32 18798456, etc. All finite decimals belong to rational numbers and can be converted into component numbers.

A simplest fraction can be converted into a decimal finite fraction 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 fraction of the base of a positive integer if and only if the prime factor of its denominator is a subset of the prime factor of the base.