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Adding fractions with unlike denominators worksheets

Twenty problems adding fractions with different denominators, such as 3/4 + 2/5, in three versions with answer keys, in simplest form.

Fraction operations: add fractions with unlike denominators

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Add. Write the answer in simplest form, as a mixed number if it is more than 1.

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Sheet AFree at teach.peabody.kids

Fraction operations: add fractions with unlike denominators

NameDate

Add. Write the answer in simplest form, as a mixed number if it is more than 1.

  1. + =
  2. + =
  3. + =
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Sheet BFree at teach.peabody.kids

Fraction operations: add fractions with unlike denominators

NameDate

Add. Write the answer in simplest form, as a mixed number if it is more than 1.

  1. + =
  2. + =
  3. + =
  4. + =
  5. + =
  6. + =
  7. + =
  8. + =
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Sheet CFree at teach.peabody.kids

Answer key

Sheet A

  1. 1
  2. 1
  3. 1
  5. 1
  7. 1
  8. 1
  10. 1
  11. 1
  20. 1

Sheet B

  1. 1
  3. 1
  5. 1
  8. 1
  10. 1
  12. 1
  13. 1
  15. 1
  18. 1
  19. 1

Sheet C

  1. 1
  3. 1
  4. 1
  5. 1
  6. 1
  7. 1
  8. 1
  11. 1
  12. 1
  15. 1
  16. 1
Answer keyFree at teach.peabody.kids

Fraction operations: 20 problems a sheet, 3 versions that do not repeat each other where the numbers allow.

How to use it

  1. Look at the sheet: it is a real, printable sheet. Switch between Sheet A, B and C, or press New numbers (N) for a fresh set.
  2. Change how many problems, how many versions, and whether the key prints. Settings stay in this browser; Share copies a link that rebuilds the same sheets.
  3. Press Print sheet A and key, or Print all. The answer key prints on its own page, so you can keep it back.

Ideas for class

  • Have students estimate against 1 or 1/2 before they start, so a result that looks wrong can be caught.
  • Teach finding a common denominator by listing multiples of the larger one until the smaller divides it.
  • Use the fraction bars on this site with the first three problems to show that renaming does not change the amount.

Related

Questions

Do the problems use the least common denominator?

The key reduces the sum to lowest terms either way, so a student may use any common denominator, such as the product of the two, and arrive at the same final answer.

Is there a matching subtraction sheet?

Yes, in the maker: choose Fraction operations and then Subtract fractions with unlike denominators. The problems are built so that the first fraction is always the larger.

Are the answer keys checked?

Each answer is worked out by the code that wrote the problem, and our tests recompute every answer a second way and compare. Please still look over the key before you grade a class set.

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What this worksheet covers

Fractions with different denominators cannot be added until the pieces are the same size. Each problem here has two denominators chosen from pairs students meet in class, such as 2 and 3, 3 and 4, 4 and 6 or 5 and 10, so some are related, where one denominator divides the other, and some are not. The key shows the sum in lowest terms, as a mixed number when it is more than one.

Who it is for

Fifth grade. Common Core 5.NF.A.1 asks students to add and subtract fractions with unlike denominators by replacing them with equivalent fractions. Students should be confident with equivalent fractions before they start.

Adding fractions that need a common denominator · grade 5

A worked example

3/4 + 2/5. A common denominator is 20. 3/4 = 15/20 and 2/5 = 8/20. Add 15/20 + 8/20 = 23/20, which is 1 3/20. The answer is greater than one, which makes sense since 3/4 is nearly one already and 2/5 adds a bit more than a third.

Mistakes to watch for

  • Adding both tops and both bottoms, so 1/2 + 1/3 becomes 2/5. Compare it with 1/2 alone: the sum should be larger.
  • Finding a common denominator but changing only one numerator. Both fractions must be renamed.

Make it your own

This sheet is one setting of the math worksheet generator. Open it there to change the skill, the range of numbers or the heading, or to mix several skills on one sheet.