Subtraction of fractions 

   1.- Subtraction of fractions with the same denominator.

   A mother has 5/9 of a bar of chocolate and she gives her daughter Elizabeth 2/9. How much chocolate does the mother have?
5/9 - 2/9 = (5-2) / 9 = 3/9. If we simplify the fraction by dividing by 3 we have: 3/9 = 1/3.

   To subtract fractions with the same denominator, we subtract the numerators, keeping the same denominator.

   Examples 6/6 - 2/6 = 4/6 = 2/3; 15/11 - 10/11 = 5/11.

   Solve these subtractions:

5/6 - 1/6 =

6/7 - 2/7 =

7/9 - 1/9 =

8/13 - 4/13 =

   2.- Subtraction of fractions with different denominator.

   To subtract fractions with different denominator, we previously reduce the fractions to a common denominator and then we subtract.

   Examples: 1/5 - 1/7 = 7/35 - 5/35 = 2/35; 1/2 - 1/3 = 3/6 - 2/6 = 1/6.

   Do these subtractions:

2/3 -1/4 =

5/6 - 3/4 =

7/9 - 1/6 =

4/5 - 1/7 =

   3.- Reduction of mixed numbers to improper fractions.

   First, we must convert the whole number to a fraction with the same denominator as the fractional part and then we add.

   Examples: 11/2 = 2/2 + 1/2 = 3/2; 3 1/4 = 12/4 + 1/4 = 13/4, 2 3/7 = 14/7 + 3 / 7 = 17/7.

   Convert these mixed numbers to improper fractions:

5 y 2/3 =

2 y 1/5 =

3 y 1/7 =

2 y 3/8 =

   4.- Subtraction of mixed numbers.

   For mixed numbers, we reduce the whole number to improper fractions and then we subtract.

   Examples: 5 1/3 - 3 2/3 = (15/3 +1 / 3) - (9/3 +2 / 3) = 16/3 - 11/3 = 5/3.

   Do these subtractions:

2 y 5/6 - 1 y 2/6 =

1 y 3/7 - 1 y 1/7 =

3 y 1/3 - 2 y 1/2 =

2 y 1/5 - 1 y 3/7 =





   5- Solve these problems:

1. An employee earns daily 35 2/7 euros and he spends 23 1/7 euros. How much money does he save daily?

2. Ana has a lot of stickers and first she gives 1/5 and then 1/4. What fraction of stickers does she have?

3. I have inherited 2/3 of a farm and I bought 1/4 of it. What fraction of the farm do I have?

4. Mary has 3 2/5 euros and Jose has 5 3/5 euros. How much money do they have in total?



 

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| Educational applications | Mathematics |
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®Arturo Ramo García.-Record of intellectual property of Teruel (Spain) No 141, of 29-IX-1999
Plaza Playa de Aro, 3, 1º DO 44002-TERUEL