adding fractions with unlike denominators
DESCRIPTION
Adding Fractions with Unlike Denominators. Common Multiple. A number that is a multiple of two or more numbers. Some multiples of 3 & 6 6, 12, 18, 24, 30, 36, 42. Least Common Multiple. The smallest common multiple of a set of two or more numbers. 5 = 5, 10, 15, 20, 25, 30. - PowerPoint PPT PresentationTRANSCRIPT
Adding Fractions Adding Fractions with Unlike with Unlike
DenominatorsDenominators
Common MultipleCommon Multiple
A number that is a A number that is a multiple of two or more multiple of two or more numbers.numbers.
Some multiples of 3 & 6
6, 12, 18, 24, 30, 36, 42
Least Common MultipleLeast Common Multiple
The smallest common The smallest common multiple of a set of two or multiple of a set of two or more numbers.more numbers.
6 = 6, 12, 18, 24, 30, 36
5 = 5, 10, 15, 20, 25, 30
Shortcut for Finding the Least Shortcut for Finding the Least Common Denominator or Least Common Denominator or Least
Common MultipleCommon Multiple
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Check to see if the smaller denominator divides evenly into the larger denominator.If it does, use the larger denominator for your LCD or LCM.
3 will divide evenly into 9, so 9 is your LCD or LCM.
To Add or Subtract To Add or Subtract Fractions With Unlike Fractions With Unlike
DenominatorsDenominators
Find the multiples of Find the multiples of each denominator.each denominator.
1= 5, 10, 15, 20, 25, 30
1= 10, 20, 30, 40, 50+
5
10
To Add or Subtract To Add or Subtract Fractions With Unlike Fractions With Unlike
DenominatorsDenominators Compare the lists of multiples. Compare the lists of multiples.
Circle the common multiples Circle the common multiples between the two lists.between the two lists.
15 = 5, 10, 15, 20, 25, 301
10 = 10, 20, 30, 40, 50+
To Add or Subtract To Add or Subtract Fractions With Unlike Fractions With Unlike
DenominatorsDenominators
Use the lowest common Use the lowest common multiple as the denominator.multiple as the denominator.
15 = 5, 10, 15 ,20 ,25 ,301
10 = 10, 20, 30, 40, 50+
To Add or Subtract To Add or Subtract Fractions With Unlike Fractions With Unlike
DenominatorsDenominators
This number is also called the This number is also called the least common denominator.least common denominator.
15 = 5, 10, 15 ,20 ,25 ,301
10 = 10, 20, 30, 40, 50+
To Add or Subtract To Add or Subtract Fractions With Unlike Fractions With Unlike
DenominatorsDenominators
Rewrite the fractions using Rewrite the fractions using the least common denominator the least common denominator or least common multiple.or least common multiple.
151
10 +
10
10
To Add or Subtract To Add or Subtract Fractions With Unlike Fractions With Unlike
DenominatorsDenominators Find the equivalent fractions Find the equivalent fractions
for 1/5 & 1/10 with 10 as the for 1/5 & 1/10 with 10 as the denominator.denominator.
151
10 +
10
10
You know that 1/10 is equal to 1/10 so
Put a 1 over theBottom 10.
1
To Add or Subtract To Add or Subtract Fractions With Unlike Fractions With Unlike
DenominatorsDenominators Find the equivalent fractions Find the equivalent fractions
for 1/5 & 1/10 with 10 as the for 1/5 & 1/10 with 10 as the denominator.denominator.
151
10 +
10
10
To find the topnumber, ask yourselfwhat do you multiply
the 5 by to get 10.1
To Add or Subtract To Add or Subtract Fractions With Unlike Fractions With Unlike
DenominatorsDenominators Find the equivalent fractions Find the equivalent fractions
for 1/5 & 1/10 with 10 as the for 1/5 & 1/10 with 10 as the denominator.denominator.
151
10 +
10
10
That’s right 2. Sinceyou are looking for
the equivalent fractionyou know the top
number must also bemultiplied by 2.
1x 2 =x 2 =
To Add or Subtract To Add or Subtract Fractions With Unlike Fractions With Unlike
DenominatorsDenominators Find the equivalent fractions Find the equivalent fractions
for 1/5 & 1/10 with 10 as the for 1/5 & 1/10 with 10 as the denominator.denominator.
151
10 +
10
10
To find the top numberjust multiply 2 x 1 toget your equivalent
fraction.1x 2 =x 2 = 2
To Add or Subtract To Add or Subtract Fractions With Unlike Fractions With Unlike
DenominatorsDenominators Now just add the Now just add the
numerators.numerators.151
10 +
10
10
Remember whenadding fractions
you never add the denominators.
1x 2 =x 2 = 2
103
Add these FractionsAdd these Fractions
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Use the shortcut to find the
Least CommonDenominator
(LCD).
8
8
Add these FractionsAdd these Fractions
1218+
Now find theequivalent
fractions for1/2 & 1/8.
8
8x 1 =
x 4 =
Ask what do you multiply 2 by to get 8and what do you multiply 8 by to get 8.
Add these FractionsAdd these Fractions
1218+
Since you arewriting equivalent
fractions, nowmultiply the topnumbers by the
same number you did in the bottom.
8
8x 1 =
x 4 =x 1 =
x 4 =
Add these FractionsAdd these Fractions
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Now multiplyacross.
8
8x 1 =
x 4 =x 1 =
x 4 =
1
4
Add these FractionsAdd these Fractions
1218+
Add yournew
numerators.
8
8x 1 =
x 4 =x 1 =
x 4 =
1
4
58
Add these FractionsAdd these Fractions
2513+
Find the common
Multiples for5 and 3. WriteThis numberAs your newdenominator.
15
15
Add these FractionsAdd these Fractions
2513+
Ask yourselfwhat you
multiply thebottom number
by to get 15.
15
15x 5 =
x 3 =
Add these FractionsAdd these Fractions
2513+
Multiply thetop numberby the samenumber you
did in thebottom.
15
15x 5 =
x 3 =x 5 =
x 3 =
Add these FractionsAdd these Fractions
2513+
Multiplyacross.
15
15x 5 =
x 3 =x 5 =
x 3 =
5
6
Add these FractionsAdd these Fractions
2513+
Now addyour new
numerators.15
15x 5 =
x 3 =x 5 =
x 3 =
5
6
1115
Add these FractionsAdd these Fractions
1614+
12
12x 3 =
x 2 =x 3 =
x 2 =
3
2
512
Add these FractionsAdd these Fractions
5618+
24
24x 3 =
x 4 =x 3 =
x 4 =
3
20
2324
Add these FractionsAdd these Fractions
2319+
9
9x 1 =
x 3 =x 1 =
x 3 =
1
6
79
Add these FractionsAdd these Fractions
4523+
15
15x 5 =
x 3 =x 5 =
x 3 =
10
12
2215
Simplify Your AnswerSimplify Your Answer
2215 15) 22
1
157
715