#### Transcript of Rational Numbers

**What is a Rational Number?**

Ratio

The word "rational" comes from the word "ratio". All fractions are numbers that are written as ratios. For example we say 2 to 3 but write 2/3. Remember, the denominator of a fraction cannot be zero. Why?

Some decimals repeat, such as 0.3333333333 . . .

An easier way to write that is as 0.33.

3/4

.5

21/2

7/8

Rational Numbers

Rational numbers are numbers that can be written as fractions.

2/3

5/8 means 5 divided by 8.

0.625

8)5.000

-48

20

-16

40

-40

0

Decimals

Any fraction can be written as a decimal by dividing the numerator by the denominator.

5/8 = 0.625

Repeating Decimals

This is called bar notation.

Decimals that

end or repeat

are rational numbers because they can be written as fractions.

Decimals to Fractions

Divide the decimal number (without the point) by 10, 100, 1000, etc., depending on how many decimal places there are.

.45= 45/100

.3 = 3/10

.675 = 675/1000

Questions

1. Where does "rational" come from?

2. Which numbers are rational?

3. How do you change a fraction to a decimal?

4. How do you indicate a repeating decimal?

5. How do we know which decimals are rational?

6. How do you change a decimal to a fraction?

7. Why can the denominator not be zero?

Full transcript