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Skills Covered

  • Write a fraction as a sum of unit fractions
  • Break a fraction apart in more than one way
  • Put parts with the same denominator back together
  • Break a fraction greater than 1 into 1 whole and the rest
  • Find a missing part of a fraction
  • List every two-part way to make a fraction

How to Use This Pack

Five pages on breaking fractions apart and putting them back together, with thirds, fourths, fifths, sixths, eighths and tenths. Page 1 shows a bar with some parts shaded, such as 3 of 4: students write 3/4 as 1/4 + 1/4 + 1/4, with a worked example first. On page 2 each fraction has two bars, each with its parts in two colors (gray and dots in black and white), and students write both ways, like 5/6 = 2/6 + 3/6 and 5/6 = 1/6 + 4/6. Page 3 turns it around: shade a bar to show 2/8 + 3/8 and write the sum, then add six short sums of unit fractions. Page 4 breaks fractions greater than 1 into a whole and the rest, like 7/4 = 4/4 + 3/4 = 1 + 3/4, then finds the missing part in six other ways to break them apart. Page 5 asks for every way to break 4/5 into two parts, and ends with three short stories about a ribbon, a pizza and cups of water.

In the Classroom

Fraction strips or paper strips folded into equal parts make this concrete: give each student 5 sixths and ask them to split the pieces into two piles in as many ways as they can, writing an equation for each. For page 4, line up 7 fourth pieces under a 1 whole strip so students see 4 fourths make 1 and 3 fourths are left. Page 5 makes a good partner check: one student colors a way, the other writes it.

At Home

Cut a sandwich or a paper strip into fourths or sixths and share the pieces between two plates in different ways: "2 sixths on this plate and 3 sixths on that one is 5 sixths in all." Measuring cups work too: three 1/4 cups of water fill a 3/4 cup.

Tips for Success

  • A unit fraction is one part: 1/4 is one of 4 equal parts
  • The bottom number stays the same when you break a fraction apart or put it together; only the parts are counted
  • Count the parts in each color to find the two parts
  • There is more than one way to break most fractions apart: check that your parts add up to the whole fraction
  • Four fourths, six sixths or eight eighths make 1 whole

Common Core Standards Alignment

This pack supports the following Common Core State Standards for Mathematics:

  • 3.NF.A.1 Know 1/b is one of b equal parts of a whole, and a/b is a of those parts (denominators 2, 3, 4, 6 and 8).
  • 3.G.A.2 Divide shapes into parts of equal area and describe each part with a unit fraction, such as 1/6 of the shape.

© Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.

Decomposing Fractions

3rd Grade

A 5-page pack for 3rd grade on breaking fractions apart and putting them back together. Write a fraction as a sum of unit fractions, like 3/4 = 1/4 + 1/4 + 1/4, read bar models that break a fraction apart two different ways, like 5/6 = 2/6 + 3/6 = 1/6 + 4/6, put two parts together and add unit fractions, break fractions greater than 1 into a whole and the rest, like 7/4 = 4/4 + 3/4 = 1 + 3/4, find every two-part way to make 4/5 and solve three short stories. Every page comes in color and in black and white. Answer keys included.

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What’s Included

  • 5 worksheets in color and in black and white, with answer keys (15 pages)
  • Sums of unit fractions with a worked example, and bars broken apart two ways
  • Put parts together with bar models, and break fractions greater than 1 into a whole and the rest
  • Find every way to make 4/5, and three short stories
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