Before adding two fractions, we need to find their common denominator. After finding the equivalent fractions and common denominators, we are able to add the fractions.
Here are the steps to follow to add fractions:
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We look for a common denominator.
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For each fraction, find an equivalent fraction.
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We only add the numerators.
||\dfrac{2}{3}+\dfrac{1}{6}||
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We look for a common denominator.
Here, the common multiple for both |3| and |6| is |6.| Thus, the common denominator is |6.| ||\dfrac{?}{6}+\dfrac{?}{6}|| -
For each fraction, find an equivalent fraction.
To convert the fractions into equivalent fractions, multiply the numerator and the denominator by the same factor. ||\begin{align}\dfrac{2}{3}=\dfrac{2\times{\color{red}2}}{3\times{\color{red}2}}=\dfrac{4}{6}\\\\\dfrac{1}{6}=\dfrac{1\times{\color{red}1}}{6\times{\color{red}1}}=\dfrac{1}{6}\end{align}|| -
We only add the numerators. ||\dfrac{4}{6}+\dfrac{1}{6}=\dfrac{4+1}{6}=\dfrac{5}{6}||
||\dfrac{7}{8}+\dfrac{2}{3}||
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We look for a common denominator.
Here, the common multiple for both |8| and |3| is |24.| Thus, the common denominator is |24.| ||\dfrac{?}{24}+\dfrac{?}{24}||
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For each fraction, find an equivalent fraction.
To convert the fractions into equivalent fractions, multiply the numerator and the denominator by the same factor.
||\dfrac{7}{8}=\dfrac{7\times{\color{red}3}}{8\times{\color{red}3}}=\dfrac{21}{24}||
||\dfrac{2}{3}=\dfrac{2\times{\color{red}8}}{3\times{\color{red}8}}=\dfrac{16}{24}|| -
We only add the numerators.
||\dfrac{21}{24}+\dfrac{16}{24}=\dfrac{21+16}{24}=\dfrac{37}{24}||
If an equation contains mixed numbers, there are two ways to solve the addition.
- Perform the operation on the integers first, then on the fractions.
||2\frac{1}{3}+3\frac{1}{3}||
First, focus on the integers: |2 + 3 = 5.|
Then the fractions, thus |\dfrac{1}{3}+\dfrac{1}{3}=\dfrac{2}{3}.|
The result is |2\dfrac{1}{3}+3\dfrac{1}{3} = 5\dfrac{2}{3}.|
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Convert the mixed numbers into fractions using the method presented above.
||\begin{align} 5\frac{1}{3}+2\frac{2}{5} &= \frac{16}{3}+\frac{12}{5} \\ &= \frac{80}{15} + \frac{36}{15} \\ &= \frac{80+36}{15} \\ &=\frac{116}{15} \\ &=7\frac{11}{15} \end{align}||
A number line can be used to illustrate a fraction.
Separate each whole on the number line into as many parts as the value of the denominator.
For example, using the fraction |\dfrac{3}{4},| the 4th line marks the whole, or the fraction |\dfrac{4}{4}.|
The steps for adding fractions are as follows:
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We look for the common denominator of the fractions.
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For each fraction, we create an equivalent fraction.
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We segment each whole on the number line into as many parts as the value of the common denominator.
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We place the 1st fraction on the number line according to its numerator.
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We add the 2nd fraction to the 1st.
We want to add |\dfrac{3}{8}+\dfrac{1}{4}.|
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We look for the common denominator of the fractions.
Here, the common denominator of |4| and |8| is |8.| -
For each fraction, we create an equivalent fraction.
To convert the fractions into equivalent fractions, we multiply the numerator and the denominator by the same factor. ||\begin{align}\dfrac{3}{8}=\dfrac{3\times{\color{red}1}}{8\times{\color{red}1}}=\dfrac{3}{8}\\\\ \dfrac{1}{4}=\dfrac{1\times{\color{red}2}}{4\times{\color{red}2}}=\dfrac{2}{8}\end{align}|| -
We segment each whole on the number line in as many parts as the value of the common denominator.
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We place the 1st fraction on the number line according to its numerator.
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We add the 2nd fraction to the 1st.
Therefore, |\dfrac{3}{8}+\dfrac{1}{4}=\dfrac{3}{8}+\dfrac{2}{8}=\dfrac{5}{8}.|
Pour valider ta compréhension des fractions de façon interactive, consulte la MiniRécup suivante :