Q: How is the number 21,205,309 written in Scientific Notation?

Why is 21,205,309 written as 2.1205309 x 10⁷ in scientific notation?

The purpose of scientific notation is for scientists to write very large, or very small, numbers with ease.

Calculating scientific notation for a positive integer is simple, as it always follows this notation:

a x 10^b

Follow the steps below to see how 21,205,309 is written in scientific notation.

Step 1

To find a, take the number and move a decimal place to the right one position.

• Original Number: 21,205,309
• New Number: 2.1205309

Step 2

Now, to find b, count how many places to the right of the decimal.

New Number:	2	.	1	2	0	5	3	0	9
Decimal Count:			1	2	3	4	5	6	7

There are 7 places to the right of the decimal place.

Step 3

Building upon what we know above, we can now reconstruct the number into scientific notation.

Remember, the notation is: a x 10^b

a = 2.1205309

b = 7

Now the whole thing:

2.1205309 x 10⁷

Step 4

Check your work:

10⁷ = 10,000,000 x 2.1205309 = 21,205,309

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