Very large and very small quantities and measures are often used to provide information in magazines, textbooks, television, newspapers and on the Internet. Some examples are:

- The distance between the sun and Neptune is 4,500,000,000 km.
- The diameter of an electron is approximately 0.00000000000022 inches.

Scientific notation is a convenient way to represent such numbers. How could you write the numbers above using scientific notation?

### Scientific Notation

To represent a number in scientific notation means to express the number as a product of two factors: a number between 1 and 10 (including 1) and a power of 10. A positive real number ‘’ is said to be written in **scientific notation** if it is expressed as where In other words, a number in scientific notation is a single nonzero digit followed by a decimal point and other digits, all multiplied by a power of 10.

When working with numbers written in scientific notation, you can use the following rules:

#### Let's write the following numbers using scientific notation:

- 2,679,000

The exponent, , represents the decimal point that is 6 places to the right of the **standard position of the decimal point.**

** **

- 0.00005728

The exponent, , represents the decimal point that is 5 places to the left of the standard position of the decimal point.

One advantage of scientific notation is that calculations with large or small numbers can be done by applying the laws of exponents.

#### Now, let's practice arithmetic operations with scientific notation. Complete the following tables:

Expression in Scientific Notation |
Expression in Standard Form |
Result in Standard Form |
Result in Scientific Notation |
---|---|---|---|

The completed table is:

Expression in Scientific Notation |
Expression in Standard Form |
Result in Standard Form |
Result in Scientific Notation |
---|---|---|---|

380,000 | |||

0.088 | |||

24,000 | |||

0.025 |

Note that the numbers in the last column have the same power of 10 as those in the first column.

Expression in Scientific Notation |
Expression in Standard Form |
Result in Standard Form |
Result in Scientific Notation |
---|---|---|---|

The completed table is:

Expression in Scientific Notation |
Expression in Standard Form |
Result in Standard Form |
Result in Scientific Notation |
---|---|---|---|

504,000 | |||

0.00275 | |||

200 | |||

0.02125 |

Note that for multiplication, the power of 10 is the result of adding the exponents of the powers in the first column. For division, the power of 10 is the result of subtracting the exponents of the powers in the first column.

#### Finally, let's calculate the following expressions involving scientific notation:

Before the rule can be used, one of the numbers must be rewritten so that the powers of 10 are the same.

Rewrite

The power indicates the number of places to the right that the decimal point must be moved to return 0.46 to the original number of 4.6.

Add the exponents of the power.

Rewrite the question and substitute with .

Apply the rule

Before the rule can be used, one of the numbers must be rewritten so that the powers of 10 are the same.

Rewrite

The power indicates the number of places to the left that the decimal point must be moved to return 47 to the original number of 4.7.

Add the exponents of the power.

Rewrite the question and substitute with .

Apply the rule

The answer must be written in scientific notation.

### Examples

#### Example 1

Earlier, you were asked to write the distance between the sun and Neptune(4,500,000,000 km) and the diameter of an electron(0.00000000000022) in scientific notation.

The distance between the sun and Neptune would be written as and the diameter of an electron would be written as .

#### Example 2

Express the following product in scientific notation:

Apply the rule

Express the answer in scientific notation.

#### Example 3

Express the following quotient in scientific notation:

Begin by expressing the numerator and the denominator in scientific notation.

Apply the rule

#### Example 4

If and , find an approximate value for . Express the answer in scientific notation.

Express all values in scientific notation.

Use the values in scientific notation to determine an approximate value for .

In the numerator, apply the rule

### Review

Express each of the following in scientific notation.

- 42,000
- 0.00087
- 150.64
- 56,789
- 0.00947

Express each of the following in standard form.

Perform the indicated operations and express the answer in scientific notation.

For the given values, perform the indicated operations for and express the answer in scientific notation and standard form.

- .

- .

### Review (Answers)

To see the Review answers, open this PDF file and look for section 6.7.