# How do you write 0.00000000129 in scientific notation?

Write down the "value" of the digits, then the number of places the decimal moved to make it happen and in this case you get
$1.29 \times {10}^{-} 9$

#### Explanation:

Scientific notation is all about telling someone 2 important bits of information: the "value" of a number - such as the digits 129 in this example, and just how many 0's are before or after it.

The value of a number will never be less than 0 and never more than or equal to 10.

So let's figure out the value - 129 is the digits we want to work with. We put the decimal point after the first digit of the value - so in this case it's 1.29.

Now let's tell people what the difference is between 0.00000000129 - the number we want to express and 1.29 - the value in our scientific notation.

We use a notation of ${10}^{x}$, where x is the number of decimal places we had to move. It's a positive number when the actual number is bigger than the value and negative when it's smaller.

Now the question is how far away from 0.00000000129 from 1.29. If I'm counting right, the decimal needs to move 9 places to the right to get from 0.00000000129 to 1.29. So 0.00000000129 is 9 decimal places smaller than 1.29. So using the notation above, it's ${10}^{-} 9$ - we had to move 9 decimal places and the actual value is smaller than the value of 1.29.

Putting it all together, the scientific notation of 0.00000000129 is a combo of the value and the number of places the decimal moved:

$1.29 \times {10}^{-} 9$