Answer:
- Both type of numbers have a decimal point but the decimal numbers can contain digits other than 0 so you have to worry for these numbers when you're multiplying and the placement of the decimal point in the answer.
- A way think about it is sum the total numbers after the decimal point, this work because the numbers can be represented as fractions (explanation below) so If one factor has 2 decimal places and another factor has 1 decimal place the answer have 3 decimal places.
Explanation:
A whole can be represented as 2.000 and so on, while a decimal number is represented as 3.14 when the numbers after the decimal point can be different of 0.
So when you multiply two decimal numbers check the total number of number after the decimal point and sum these amounts.
Example:
Suppose the next two numbers 12.88 and 3.1 both have different amounts of number after the decimal point, but with the simplification we can see that the final answer contain 3 decimal places.
But, why this work? Well remember that a decimal can be represented as a fraction of this way
So if you does the product of these fractions you get the next value:
Where the total number of numbers after the decimal point is equal to the power of 10 in the denominator that's mean equal to 3. However this method take more time, so is more simply say that the total of numbers after the decimal point is the sum of the total of numbers after the decimal point of each decimal number.