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Multiplication of decimal rational numbers


Consider the following multiplication:

3,49 · 2,5.

Transforming into decimal fractions we have:

Practical method:

We multiply the two decimal numbers as if they were natural. We put the comma in the result so that the number of decimal places in the product is equal to the sum of the factor's decimal places.

Examples:

3,49 · 2,5

1,842 · 0,013

Note:

1. In the multiplication of one natural number by a decimal number, we use the practical method of multiplication. In this case, the number of decimal places in the product is equal to the number of decimal places in the decimal factor. Example:

5 · 0,423 = 2,115

2. To multiply a decimal number by 10, 100, 1,000,…, just move the comma to the right one, two, three,…, decimal places. Examples:

3. Decimal numbers can be turned into percentages. Examples:

0,05 = = 5%

1,17 = = 117%

5,8 = 5,80 = = 580%

Next: Exact Division