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Math – How Do I Add Fractions?

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Adding fractions isn’t as difficult as it seems if you get your child to actually think about what it is he is adding.

You can give your child the following example in order to help him/her understand fractions.

Assume you have a pack of 100 crayons and you give your friend 5 crayons, or 5/100 of the pack, and you give another friend 2 crayons, or 2/100 of the pack. You have now given away 7 crayons out of 100, or 7/100 because,

5/100 + 2/100 = 7/100.

It is important to notice that you add the numerators (i.e. the numbers on top, in this example they are 5 and 2) but NOT the denominators.

This is all and well if the denominators are the same, but what if they are different?

Let’s assume you want to add 1/3 of a pizza with 2/5 of a pizza. You would have to add the fractions 1/3 + 2/5.

You can’t add fractions with different denominators.

You do this by changing the denominators so that they are the same. This is referred to as finding a common denominator. A common denominator is a number that is divisible by both denominators of the fractions that we are adding. In this case, we want to find a common for the denominators 3 and 5. We can list the factors of 3 and 5:

3, 6, 9, 12, 15, 18, 21, 24, 27, 30

5, 10, 15, 20, 25, 30

We can use 30 because 30 is common to both 3 and 5, but it is best to use the lowest common multiple. So we will use 15.

If we change the denominator, 3, to 15, we multiply by 5. So we must do the same for the top, 1 x 5 = 5. Now we have changed 1/3 to 5/15. If we do the same to 2/5 we get 6/15.

Now it’s easy to add because 5/15 and 6/15 have the same denominator. Our answer is 11/15.

You can show your child how to add fractions with the same denominator, that’s easy. If the denominators are not the same, find a common denominator, change the numerator and denominator, and then add.

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Tutorgiant.com provides complete Fractions lessons with worksheets.

See some of the lessons in our video library.

FRACTIONS - Lesson (A) Introduction to Fractions (Grades 1-2)

FRACTIONS - Lesson (B) Fractions of Sets (Grade 3)

FRACTIONS - Lesson (C) Comparing Fractions (Grade 3)

FRACTIONS - Lesson (D) Equivalent (Grades 4-5)

FRACTIONS - Lesson (E) Equivalent (Numerical) (Grades 4-5)

FRACTIONS - Lesson (F) Changing Fractions to Decimals (Grades 4-5)

FRACTIONS - Lesson (F2) Changing Fractions to Decimals Using Division (Grades 5-6)

FRACTIONS - Lesson (G) Changing Decimals into Fractions (Grades 4-6)

FRACTIONS - Lesson (H) Comparing (Grade 5)