Best Answer

When multiplying decimals, the decimal points are not only not aligned they are completely removed from the numbers to leave a multiplication of whole numbers which is done.

Then the decimal point is put back into the answer by counting how many digits in total were after the decimal points in the original numbers and making the answer have the same number of digits after the decimal point.

Example:

1.23 x 45.6 → 123 x 456 = 56088

1.23 has 2 digits after the decimal point,

45.6 has 1 digit after the decimal point

making a total of 2 + 1 = 3 digits after the decimal point in the question, so there must be 3 digits after the decimal point in the answer

→ 1.23 x 45.6 = 56.088

Second example:

1.25 x 3.4 → 125 x 34 = 4250

2 digits + 1 digit = 3 digits in total in question must be after decimal point in answer:

→ 1.25 x 3.4 = 4.250

but normally any zeros that come at the end of a number after a decimal point are not written, so this would normally be written as:

1.25 x 3.4 = 4.25

A decimal number is a whole number divided by a power of 10, that is 10, 100, 1000, etc.

This means that a decimal number can be written as an improper fraction with a power of 10 as the bottom number.

So for the first example:

1.23 = 123/100

45.6 = 456/10

Multiplying the decimals together is the same as multiplying the two fractions together, which is done by multiplying the top numbers together and multiplying the bottom numbers together:

1.23 x 45.6 = 123/100 x 456/10

= (123 x 456)/(100 x 10)

= 56088/1000

= 56.088

Q: Why isn't decimal numbers aligned when multiplying decimals?

Write your answer...

Submit

Still have questions?

Continue Learning about Math & Arithmetic

No, it is not true.

Lets say that u r doing the problem. 5.2 x 2.1 there are altogether 2 numbers to the right of the decimal, so you take out the decimals, multiply, and add the decimal 2 numbers to the left.

It depends on what numbers you are multiplying and how many decimals places they each have. It doesn't always haveto move to the right.

Very.

If two decimal number have X and Y decimal places, respectively, then the raw product (before removing any trailing zeros) of the two numbers will have (X + Y) decimal places.

Related questions

The answer depends on the decimal numbers: there is no simple answer if one (or both) of the decimals is a non-terminating number.

It is the multiplication of numbers where one or more of the multiplicands is in decimal form.

No, it is not true.

You do the multiplication in exactly the same way. The only extra thing is that when multiplying decimals, you need to place the decimal point (or decimal comma - depending on your country) in the correct position. If one number has, for example, 3 digits after the decimal point, and the other 4, you need to place the decimal point in the result (BEFORE eliminating unnecessary zeros) in such a way that there are, in this example, 7 digits (3 + 4) to the right of the decimal point.

Adding whole numbers is the addition of decimals where the decimal part is zero; in both cases the digits are place value aligned meaning that the decimal points, which lies between the units (or ones) and tenths columns, are aligned - in the whole number the decimal point is "hiding" at the end.

You write them, one below the other, with their decimal points aligned.

The main difference is that with whole numbers the decimal point is "hiding" (after the last digit of each whole number) whereas with decimal numbers it is clearly visible. In both cases the numbers are added with the decimal points aligned - with whole numbers there are no digits after the decimal points so the decimal points are not written, but if they were they would be visible after the last digit of the whole numbers and they would be automatically aligned; with decimal numbers there may be a different number of digits after each decimal point so it is up to the person doing the arithmetic to ensure the decimal points are aligned.

Lets say that u r doing the problem. 5.2 x 2.1 there are altogether 2 numbers to the right of the decimal, so you take out the decimals, multiply, and add the decimal 2 numbers to the left.

Fractions and decimals are usually rational numbers. Besides, multiplying rational and irrational numbers is also similar.

The fundamental operations on whole numbers and decimals are addition, subtraction, division, and multiplication. However, multiplying and dividing decimals is a bit more complicated because you have to count decimal points to get an accurate answer.

If two decimal numbers have x and y digits after the decimal point respectively, then their product has (x + y) digits after the decimal point.

It depends on what numbers you are multiplying and how many decimals places they each have. It doesn't always haveto move to the right.