Decimals are a way of expressing fractions in an equivalent form that's often easier to work with.

For example, let's consider the fraction "one-tenth":

\dfrac{1}{10}

To express this fraction as a decimal, we write a zero ({\color{red}0}) followed by a dot (\,.) (called the decimal point) followed by the fraction's numerator:

\dfrac{\color{blue}1}{10} = {\color{red}{0}}{\color{blue}{.1}}

Any fraction with a denominator of 10 can similarly be written as a decimal.

For example, we can express six-tenths as a decimal as follows: \dfrac{\color{blue}6}{10} = 0.{\color{blue}{6}}

Note: Fractions with a denominator of 10 are examples of decimal fractions. We'll meet more decimal fractions in this lesson.

FLAG

Which decimal number is equivalent to \dfrac{8}{10}?

EXPLANATION

Since we have a denominator of 10, we can write this fraction as a decimal as follows:

\begin{align*} \dfrac{\color{blue}8}{10} &=0.{\color{blue}{8}} \end{align*}

FLAG

Which decimal number is equivalent to $\dfrac{7}{10}?$

a
$0.17$
b
$0.14$
c
$0.77$
d
$0.07$
e
$0.7$

$\dfrac{3}{10}=$

a
$3.1$
b
$0.33$
c
$0.31$
d
$0.03$
e
$0.3$

Fractions with a denominator of 100 can also be written as decimals. For this reason, they are also called decimal fractions.

When writing a fraction with a denominator of 100, we must remember the following crucial fact:

Every fraction with a denominator of 100 will have precisely two digits after the decimal point.

Let's see some examples:

  • We express the fraction seventy-eight hundredths as a decimal as follows: \dfrac{\color{blue}78}{100} = 0.{\color{blue}78} Notice that this decimal has two digits after the decimal point.

  • We express the fraction three-hundredths as a decimal as follows: \dfrac{\color{blue}3}{100} = 0.0{\color{blue}3} Notice that this decimal also has two digits after the decimal point.

Watch Out! When the numerator is smaller than 10, we must write an extra zero after the decimal point and before the numerator's digit. The following answers are not equivalent to \dfrac{3}{100}{:}

0.3, \qquad 0.30, \qquad 00.3

Finally, the fraction \dfrac{1}{100} is known as one-hundredth, and can also be written as a decimal:

\dfrac{\color{blue}1}{100} = 0.0{\color{blue}{1}}

FLAG

What is \dfrac{25}{100} written as a decimal?

EXPLANATION

Since we have a denominator of 100, we can write this fraction as a decimal with 2 decimal places:

\dfrac{\color{blue}25}{100} = 0.{\color{blue}25}

FLAG

$\dfrac{54}{100}=$

a
$0.504$
b
$0.018$
c
$0.054$
d
$0.54$
e
$0.108$

$\dfrac{3}{100}=$

a
$0.03$
b
$0.31$
c
$0.3$
d
$0.33$
e
$0.301$

Any fraction with a denominator of 1,000 can be written as a decimal with 3 decimal places, in the same way as before. Fractions with a denominator of 1,000 are another example of decimal fractions.

Some examples of decimal fractions with denominator 1,000 are shown below:

\dfrac{\color{blue}125}{1,000} = 0.{\color{blue}{125}} \qquad \dfrac{\color{blue}65}{1,000} = 0.0{\color{blue}{65}} \qquad \dfrac{\color{blue}7}{1,000} = 0.00{\color{blue}{7}}

The fraction \dfrac{1}{1,000} is known as one-thousandth, and can also be written as a decimal:

\dfrac{\color{blue}1}{1,000} = 0.00{\color{blue}{1}}

FLAG

Find the decimal number equivalent to \dfrac{32}{1,000}.

EXPLANATION

Since we have a denominator of 1,000, we can express this fraction as a decimal with 3 decimal places:

\dfrac{\color{blue}{32}}{1,000} = 0.0{\color{blue}{32}}

FLAG

$\dfrac{125}{1,000} =$

a
$0.008$
b
$0.080$
c
$0.521$
d
$0.125$
e
$0.012$

$\dfrac{5}{1,000} =$

a
$0.2$
b
$0.105$
c
$0.05$
d
$0.02$
e
$0.005$
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