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FRACTIONS

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FRACTIONS Adding & Subtracting Fractions with Different Denominators By Timothy Leonard Fractions with Same (Common) Denominators It's easy to add and subtract like ... – PowerPoint PPT presentation

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Title: FRACTIONS


1
FRACTIONS
  • Adding Subtracting Fractions with Different
    DenominatorsBy Timothy Leonard

2
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
3
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).

4
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.

?
?

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
5
Subtracting Fractions with Different Denominators
14
13
-

?
  • 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.

6
Subtracting Fractions with Different Denominators
(contd)
?
14
13
-

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
-

7
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

8
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
9
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
10
Incorrect
  • Did you forget to make them equivalent fractions?

?
11
Correct
  • Great Job, move to the next question.

?
12
Incorrect
  • Did you forget to subtract or did you forget to
    make them equivalent?

?
13
Correct
  • Great Job, move to the next question.

?
14
CorrectDone w/Adding, Now Lets Try Something
New
  • Great Job, move to the next question.

?
15
Excellent Job
  • For further practice or explanations on adding
    and subtracting fractions, here are some
    suggested websites.

?
16
For Further Study
  • http//www.visualfractions.com/
  • http//www.shodor.org/interactivate/activities/Fra
    ctionSorter/?versionskip1browserunknown
  • http//www.funbrain.com/
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