Adding Fractions with Unike Denominators

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Adding Fractions With Unlike Denominators
Presentation by Jennifer Fairfield
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Math
SCS Objective 1.02
Develop fluency in adding and subtracting
non-negative rational numbers.
a. Develop and analyze strategies for adding and
subtracting numbers.
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I went to the store and bought 3/4 pound of ham
and 2/3 pound of salami. How many pounds of meat
did I buy in all?
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First, write a number sentence to solve the
problem.
3/4 2/3 n
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Can you add 3/4 2/3 n as it is right now?
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No, the fractions have different denominators, 4
and 3.
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Now, I have to find the Least Common Multiple
(LCM) of 4 and 3. This is my Least Common
Denominator (LCD).
4 4, 8, 12, 16, 20 3 3, 6, 9, 12, 15
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Use the LCD (12) to make equivalent fractions.
3/4 x 3/3 9/12 2/3 x 4/4 8/12
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Next, add your new equivalent fractions.
9/12 8/12 17/12
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17/12 is an improper fraction. You must change
it to a mixed number using division.
17
12 1r5 1 5/12
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Now I know how many pounds of meat I bought. 3/4
lb. 2/3 lb. 1 5/12 lbs. of meat.