Grade 4 - Progress in Mathematics

Add Fractions: Unlike Denominators

9-7

Mitchell hiked from camp to Crystal Cave

and then to Cedar Lake. How far did Mitchell hike?

To find how far he hiked,

add: 
 170 

^12 

To add fractions with

unlike denominators:

• First find the LCM.


• Use the LCM to rename
  as fractions with like
  denominators.


• Then add the like fractions.


 1

7

0 


1

2





5


 5 
 1

7

0 
 
 1

7

0 
 
 1

7

0 


.


1

2 
.

1

2





5


 5 
 1

5


 0 
 1

5

0 
 
 1

5

0 





1

1

2

0 
 

1

1

2

0 
^1 
 1

2

0 
^1 

1

5 

Mitchell hiked 1
^15 
miles.

Study these examples.


^14 

^14 
^22 
^28 
 
^46 

^13 
^22 
^46 
 
^34 
 
^34 
 33 
 192 


^38 

^14 
^22 
^38 
 
^13 

^13 
^22 
^26 
 
 112 

^34 
 33 
 112 


^38 

^14 
 22 
^58 
 
^13 

^13 
^22 
^66 
 1 
 112 

^34 
 33 
^1102 

^56 

Crystal Cave

Camp

Cedar Lake

107 mile^12 mile

Multiples of 2: 2, 4, 6, 8, 10 , 12...

Multiples of 10: 10 , 20,...

LCM of 2 and 10: 10

Rename the fractions.

Add the numerators.

Write the like

denominator.

Write the sum

in simplest form.

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