SUBTRACTING FRACTIONS WITH UNLIKE DENOMINATORS WORKSHEET

Problem 1 : 

Find the value of : 

3/5 - 2/3

Problem 2 : 

Find the value of : 

7/12 - 5/18

Problem 3 : 

Find the value of : 

1/8 + 5/6 - 7/18

Problem 4 : 

Find the value of : 

1/4 - 1/5 - 1/10

Detailed Answer Key

Problem 1 : 

Find the value of : 

3/5 - 2/3

Solution : 

Find the LCM (Least common multiple) of the denominators.

LCM of (5, 3)  =  15

Now, make the denominator of each fraction as 15 using multiplication and subtract the fractions with like denominators. 

Then, we have  

3/5 - 2/3  =  (3 ⋅ 3)/(5 ⋅ 3) - (2 ⋅ 5)/(3 ⋅ 5)

3/5 - 2/3  =  9/15 - 10/15

3/5 - 2/3  =  (9 - 10) / 15

3/5 - 2/3  =  -1/15

Problem 2 : 

Find the value of : 

7/12 - 5/18

Solution : 

Find the LCM (Least common multiple) of the denominators.

LCM of (12, 18)  =  36

Now, make the denominator of each fraction as 36 using multiplication and subtract the fractions with like denominators. 

Then, we have  

7/12 - 5/18  =  (7 ⋅ 3)/(12 ⋅ 3) - (5 ⋅ 2)/(18 ⋅ 2)

7/12 - 5/18  =  21/36 - 10/36

7/12 - 5/18  =  (21 - 10) / 36

7/12 - 5/18  =  11/36

Problem 3 : 

Find the value of : 

1/8 + 5/6 - 7/18

Solution : 

Find the LCM (Least common multiple) of the denominators.

LCM of (8, 6, 18)  =  72

Now, make the denominator of each fraction as 72 using multiplication and simplify the fractions with like denominators. 

Then, we have  

1/8 + 5/6 - 7/18  =  9/72 + 60/72 - 28/72

1/8 + 5/6 - 7/18  =  (9 + 60 - 28) / 72

1/8 + 5/6 - 7/18  =  41/72

Problem 4 : 

Find the value of : 

1/4 - 1/5 - 1/10

Solution : 

Find the LCM (Least common multiple) of the denominators.

LCM of (4, 5, 10)  =  20

Now, make the denominator of each fraction as 20 using multiplication and simplify the fractions with like denominators. 

Then, we have  

1/4 - 1/5 - 1/10  =  5/20 - 4/20 - 2/20

1/4 - 1/5 - 1/10  =  (5 - 4 - 2) / 20

1/4 - 1/5 - 1/10  =  -1/20

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