How do you solve multiplication problems with decimals without a calculator?

Answer 1

If you can do multiplication of two integers without a calculator, then you can multiple an integer (a whole number) with a floating-point number (a number with decimals) without a calculator too.

For example, let us say you want (2.56 * 5).

2.56 * 5

= 2.56 * 5 /1 (I am not changing any value)

= 256 * 5 /100 (I am multiplying the numerator and denominator by 100)

= 1280 /100 (do my multiplication of two integers, 256 and 5)

= 12.8 (do the division)

Note that I am doing the process in the long-hand for illustration purpose. You can take short-cuts once you are comfortable with the process. For example, I shall go straight to multiplying 256 with 5 (ignoring the decimal point; it is like moving the decimal point two places to the right), get the answer, and then move the decimal point two places to the left to return the decimal point to the right location.

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Answer 2

It's easier then you think. First solve it without the decimal in it. then count how many decimals are behind it for both numbers and add it in later.

Here's an example because I'm not good at explaining.

```2.4

`x`5.3

----------

Take out decimals:

```24

`x`53

-----------

1272

easier? now solve it

Because there were one number behind the decimal for both number you add the decimal two spots from right to left

12.72 -- that's your answer try it around and practice.

Heres another example:

34.54

x60.3

---------

?

3454

x603

---------

2082762

2082.762 get it? All you need is practice