Adding and Subtracting Fractions

1
Adding and Subtracting Fractions

• By Maren Miller

2
Review

• What is a numerator?
• What is a denominator?
• What does a normal fraction look like?
• What does a improper fraction look like?
• What does a mixed number look like?

3
Like Fractions

• When fractions have the same denominator they are
  like fractions.
• You can add or subtract fractions when you have
  like fractions.
• These are all like fractions.

4 7 6 3 2
5 5 5 5 5
5 5
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Adding Like Fractions

• Steps
• Make sure that you have like fractions.
• Add the numerators.
• Write the sum over the denominator.
• Write the answer in simplest form.

1 6
4 6
5 6
The answer is 5 6
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Subtracting Like Fractions

• Steps
• Make sure that you have like fractions.
• Subtract the numerators.
• Write the difference over the denominator.
• Write the answer in simplest form.

7 8
3 8
4 8
The answer is 1 2
6
Exercise 1 Add or subtract, simplify, use mixed
numbers
1/5
2 1/4

1. 1/5 2/5
2. 2/3 - 1/3
3. 3/4 2/4
4. 5/7 3/7
5. 3/2 - 1/2
6. 3/9 5/9
7. 2/8 - 2/8

8. 4/5 - 3/5 9. 7/8 3/8 10. 2/6
3/6 11. 5/10 - 3/10 12. 6/7 4/7 13. 9/12
3/12 14. 2/7 - 1/7
15. 12/4 - 3/4 16. 3/6 9/6 17. 4/13 -
2/13 18. 7/9 - 1/9 19. 8/16 - 4/16 20.
2/3 5/3
3/5
1 2/8
2
1/3
5/6
2/13
1 1/4
1 2/7
1/5
8/9
1
1 3/7
1/4
8/9
1
2 1/3
0
1/7
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Unlike Fractions

• Unlike fractions have different denominators.
• Adding or subtracting with unlike fractions
  isnt that different from adding or subtracting
  like fractions. You just have to find what their
  denominators have in common.

2 3
5 6
5 8
3 4
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Changing Unlike to Like

• Steps
• Find a common multiple that will go into both
  denominators.
• Multiply the numerator and denominator by the
  same number so the denominator is the same as the
  common multiple.
• WHAT EVER YOU DO TO THE BOTTOM YOU HAVE TO DO TO
  THE TOP!

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2 3
Now youre ready to use these fractions for
addition and subtraction!
3, 6, 9, 12, 15, 18
6
6
5 6
5
6, 12, 18, 24, 30, 36
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Exercise 2 Add fractions, put them in simplest
form

1. 1/2 1/3
2. 1/3 1/5
3. 5/6 1/3
4. 1/8 3/4
5. 3/3 5/6

1. 3/4 3/20
2. 6/7 3/4
3. 1/9 2/3
4. 3/6 2/9
5. 1/6 5/12

5/6
9/10
8/15
1 17/28
7/9
1 1/6
7/8
13/18
7/12
1 5/6
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Exercise 3 Subtract fractions, put them in
simplest form

1. 1/5 - 2/5
2. 1/4 - 1/6
3. 7/8 - 2/3
4. 4/5 - 3/10
5. 8/9 - 1/3

1. 3/5 - 1/3
2. 1/3 - 1/6
3. 9/10 - 2/5
4. 2/3 - 1/2
5. 4/5 - 1/3

1/10
4/15
1/12
1/6
5/24
1/2
1/2
1/6
7/15
5/9
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Improper Fractions

• Improper fractions are easy!
• Just treat them as if theyre normal fractions.
• Thats it!

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Unlike Improper Fractions
15/6
5/2
4/3
8/6
7/6
or
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Mixed Numbers

• There are two ways to change mixed numbers so you
  can add or subtract.
• Change the mixed number into an improper
  fraction.
• Change just the fraction and leave the whole
  number alone.

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Mixed Numbers

• 1

1/5

• Steps
• Add the fractions together.
• Add the whole numbers.

2
3/5
The answer is 3 4/5
3
4/5
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Unlike Mixed Numbers

• Steps
• Change the unlike fractions to like fractions.
• Add the fractions.
• Add the whole numbers.
• If the fraction is improper, change it to mixed
  and add the whole numbers.

• 1

2
5/6
5/6
1/2
1/2
The answer is 4 1/3
4
3
1
2/6
8/6
3/6
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Exercise 4 Add or subtract, write in simplest
form

1. 1 3/8 - 11/8
2. 2 2/5 1 1/5
3. 1 7/8 1 6/8
4. 3 4/7 2 3/7
5. 4 8/9 - 2 1/9

1. 2 2/5 1 1/10
2. 3 1/4 2 1/2
3. 5 2/3 3 1/2
4. 3 5/6 1 3/5
5. 6 1/4 - 3 2/3

1/4
3 1/2
3/4
3 3/5
1/8
9 1/6
2 7/30
6
10
2 7/9