FRACTIONS

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FRACTIONS

• Adding Subtracting Fractions with Different
  DenominatorsBy Timothy Leonard

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Fractions with Same (Common) Denominators

• It's easy to add and subtract like fractions, or
  fractions with the same denominator.
• You just add or subtract the numerators and keep
  the same denominator.

2/4 (or ½)
1/4
1/4
2/5
- 1/5
3/5
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Denominators that are multiples of another

• To Add and Subtract Fractions with different
  denominators, you need to know how to find the
  least common denominator (LCD).
• To find the least common denominator find the
  least common multiple of the denominators.

• In the above addition problem the multiples of
  each denominator are

• 15 is the least common multiple (lowest shared
  number) between the two sets of multiples and is
  your least common denominator (LCD).

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Adding Fractions with Different Denominators
(contd)

• Now that youve found your least common
  denominator (15), ask yourself how many times
  does each starting denominator go into 15.

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1/5
2/3
15
155 3 and 153 5

• Now multiply each result times the corresponding
  numerator.

3x1 and 5x2
3
10

• Answer

10

3
13

15
15
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Subtracting Fractions with Different Denominators
14
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-

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• Its difficult to determine the exact answer
  using this animation of 1/3 1/4. Now attempt
  to solve using least common denominator method.
  Lets take a look at the next slide.

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Subtracting Fractions with Different Denominators
(contd)
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13
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WHOLE
Now we have twelfths
Multiples of 3 3, 6, 9, 12, 15Multiples of 4
4, 8, 12, 16Least common multiple 12
Multiply numerators by 1234 and 1243,
respectively
112
312
412
-

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Denominators that are multiples of each other

• To Add and Subtract Fractions with different
  denominators which are multiples of each other,
  you have fewer steps to find the least common
  denominator (LCD).
• To find the least common denominator in this
  instance the greater of the 2 denominators
  becomes the LCD.

10 is a multiple of 5, and 10 is also a multiple
5, 10, 15, 20, 25

• Now only 1 division and 1 multiplication
  operation is required

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Give It a TryLets Practice Adding Fractions
Number 1 2/6 2/3 ? 2/6 2/3 ?
a) 1/3
b) 1
c) 2/6

Number 2 2/6 1/6 ? 2/6 1/6 ?
a) 4/6
b) 3/5
c) 1/2

Number 3 3/8 2/8 ? 3/8 2/8 ?
a) 5/8
b) 3/8
c) 1/8

Number 4 3/8 2/6 ? 3/8 2/6 ?
a) 5/14
b) 6/24
c) 17/24
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What Has Been Given,We Now Have to Take
Away.Its Time to Practice Subtracting Fractions
Number 1 2/3 - 2/6 ? 2/3 - 2/6 ?
a) 2/3
b) 1/3
c) 1/2

Number 2 2/6 - 1/6 ? 2/6 - 1/6 ?
a) 3/6
b) 1/2
c) 1/6

Number 3 3/8 - 1/8 ? 3/8 - 1/8 ?
a) 1/8
b) 3/8
c) 1/4

Number 4 3/8 - 2/6 ? 3/8 - 2/6 ?
a) 1/24
b) 5/14
c) 1/6
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Incorrect

• Did you forget to make them equivalent fractions?

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Correct

• Great Job, move to the next question.

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Incorrect

• Did you forget to subtract or did you forget to
  make them equivalent?

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Correct

• Great Job, move to the next question.

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CorrectDone w/Adding, Now Lets Try Something
New

• Great Job, move to the next question.

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Excellent Job

• For further practice or explanations on adding
  and subtracting fractions, here are some
  suggested websites.

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For Further Study

• http//www.visualfractions.com/
• http//www.shodor.org/interactivate/activities/Fra
  ctionSorter/?versionskip1browserunknown
• http//www.funbrain.com/