4th Grade Adding and Subtracting Fractions and Mixed Numbers Worksheet Answer Key (PDF)

$4th grade adding fractions worksheet answers – Maths PDF$

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This 4th grade adding fractions worksheet answers covers adding and subtracting fractions and mixed numbers (Common Core 4.NF.B.3a, 4.NF.B.3b, 4.NF.B.3c, 4.NF.B.3d), with a free PDF to print.

Key takeaway: This answer key helps fourth grade students and parents check fraction and mixed number work step by step.

Topic: Adding and Subtracting Fractions and Mixed Numbers (4th grade)
Content: Step-by-step answers to 20 worksheet problems
Standards: 4.NF.B.3a, 4.NF.B.3b, 4.NF.B.3c, 4.NF.B.3d
Answers: Every step shown, with the method to review
Format: Free printable PDF, US Letter, black and white

This answer key helps fourth grade students and parents check fraction and mixed number work step by step. Also, each solution shows the numerators being added or subtracted, the denominator staying the same, and any regrouping that follows.

The key covers all 20 worksheet problems. Then, solutions to problems 7 to 14 show every conversion between mixed numbers and improper fractions, and the word problem answers include units such as miles, feet, cups, and yards. When an answer is not simplified or not in mixed form, the key says so. Also, spend about 15 minutes comparing, and rework any problem that does not match.

Use this answer key to check each problem on the adding and subtracting fractions worksheet. Every solution shows the regrouping or the conversion between mixed numbers and improper fractions, step by step.

Grade 4 · Common Core State Standards: 4.NF.B.3a, 4.NF.B.3b, 4.NF.B.3c, 4.NF.B.3d

4th grade adding fractions worksheet answers: worksheet problems 1 to 10

1 – Add eighths

Add the numerators and keep the denominator: $2 + 3 = 5$.

Answer: $\frac{5}{8}$.

2 – Add tenths

$4 + 5 = 9$, and the denominator stays 10.

Also, Answer: $\frac{9}{10}$.

3 – Subtract twelfths

$7 – 2 = 5$.

Answer: $\frac{5}{12}$.

4 – Missing numerator

The sum is 11 twelfths and one part is 5 twelfths, so subtract: $11 – 5 = 6$.

Check: $\frac{6}{12} + \frac{5}{12} = \frac{11}{12}$.

Answer: 6.

5 – Unit fractions

A unit fraction has numerator 1. Three fourths is 3 pieces of $\frac{1}{4}$.

Answer: $\frac{3}{4} = \frac{1}{4} + \frac{1}{4} + \frac{1}{4}$.

6 – Decompose five sixths

Split 5 into two numbers: 1 + 4 and 2 + 3.

Answer: $\frac{5}{6} = \frac{1}{6} + \frac{4}{6}$ and $\frac{5}{6} = \frac{2}{6} + \frac{3}{6}$.

7 – Sum greater than 1

$5 + 6 = 11$, so the sum is $\frac{11}{8}$.

$11 \div 8 = 1$ remainder 3, so $\frac{11}{8}$ = $1\frac{3}{8}$.

Answer: $1\frac{3}{8}$.

8 – Mixed number to fraction

$2 = \frac{6}{3}$, so $\frac{6}{3} + \frac{1}{3} = \frac{7}{3}$.

Seven thirds in all.

Answer: $\frac{7}{3}$.

9 – Fraction to mixed number

$11 \div 4 = 2$ remainder 3.

Answer: $2\frac{3}{4}$.

Worksheet problem 10 and after

10 – Add mixed numbers

Wholes: $3 + 2 = 5$. Fractions: $\frac{1}{10} + \frac{6}{10} = \frac{7}{10}$.

Answer: $5\frac{7}{10}$.

Worksheet problems 11 and up

11 – Regroup after adding

Wholes: $3 + 1 = 4$. Fractions: $\frac{5}{6} + \frac{4}{6} = \frac{9}{6} = 1\frac{3}{6}$.

$4 + 1\frac{3}{6} = 5\frac{3}{6}$.

Answer: $5\frac{3}{6}$.

12 – Subtract mixed numbers

Wholes: $4 – 2 = 2$. Fractions: $\frac{7}{8} – \frac{3}{8} = \frac{4}{8}$.

Answer: $2\frac{4}{8}$.

13 – Subtract with regrouping

$7\frac{2}{6} = \frac{44}{6}$ and $3\frac{5}{6} = \frac{23}{6}$.

$\frac{44}{6} – \frac{23}{6} = \frac{21}{6} = 3\frac{3}{6}$.

Also, Answer: $3\frac{3}{6}$.

14 – Whole minus mixed

$6 = \frac{30}{5}$ and $2\frac{3}{5} = \frac{13}{5}$.

$\frac{30}{5} – \frac{13}{5} = \frac{17}{5} = 3\frac{2}{5}$.

Answer: $3\frac{2}{5}$.

15 – Weekend runs

$\frac{3}{8} + \frac{4}{8} = \frac{7}{8}$.

The total is $\frac{7}{8}$ mile.

Answer: $\frac{7}{8}$ mile.

16 – Pizza left

The whole pizza is $\frac{12}{12}$. $\frac{12}{12} – \frac{5}{12} = \frac{7}{12}$.

Answer: $\frac{7}{12}$ of the pizza.

17 – Two boards

Wholes: $2 + 1 = 3$. Fractions: $\frac{3}{10} + \frac{8}{10} = \frac{11}{10} = 1\frac{1}{10}$.

$3 + 1\frac{1}{10} = 4\frac{1}{10}$.

Answer: $4\frac{1}{10}$ feet.

Worksheet problem 18 and after

18 – Flour left

$4\frac{1}{3} = \frac{13}{3}$ and $1\frac{2}{3} = \frac{5}{3}$.

$\frac{13}{3} – \frac{5}{3} = \frac{8}{3} = 2\frac{2}{3}$.

The missing part is 2 $\frac{2}{3}$ cups.

Answer: $2\frac{2}{3}$ cups.

19 – Ethan's walk

Wholes: $1 + 2 + 1 = 4$. Fractions: $\frac{1}{4} + \frac{2}{4} + \frac{3}{4} = \frac{6}{4} = 1\frac{2}{4}$.

$4 + 1\frac{2}{4} = 5\frac{2}{4}$.

Answer: $5\frac{2}{4}$ miles.

20 – Ribbon

Used: wholes $1 + 2 = 3$, fractions $\frac{3}{8} + \frac{4}{8} = \frac{7}{8}$, so $3\frac{7}{8}$ yards.

Left: $5 = \frac{40}{8}$ and $3\frac{7}{8} = \frac{31}{8}$, so $\frac{40}{8} – \frac{31}{8} = \frac{9}{8} = 1\frac{1}{8}$.

The ribbon that is left is 1 $\frac{1}{8}$ yards.

Answer: $1\frac{1}{8}$ yards.

Key facts behind this 4th grade adding fractions worksheet answers

Key facts

With like denominators, add or subtract the numerators and keep the denominator.
Next, a fraction can be decomposed in more than one way, such as 5/6 = 2/6 + 3/6.
A mixed number such as 2 1/4 equals the improper fraction 9/4.
Then, to add mixed numbers, add the wholes and the fractions, then regroup when the fraction is greater than 1.
To subtract mixed numbers, change them to improper fractions first.

Common mistakes with this 4th grade adding fractions worksheet answers

Students compare only the final fraction and miss when the form is different. An answer of $\frac{11}{8}$ and one of $1\frac{3}{8}$ are equal, so check before marking it wrong.
Students skip the regrouping steps in problems 11 and 13. Those steps explain where the new whole comes from, so read them before the answer.
Students forget units in word problems. Also, problems 15 to 20 need miles, slices or fractions of a pizza, feet, cups, and yards in the final answer.
Students fix an answer by copying the key. Instead, cover it, redo the problem from the start, and compare only after you have a new answer.

How to use these solutions

Mark each answer with a check or a dot, then redo the dotted problems on a new sheet. Finally, fewer problems make the review feel manageable.
Look at the pattern in your errors. Also, if most are in mixed number subtraction, practice problems 12 to 14 again before moving on.
Parents can ask the child to explain how the denominator stays the same in one solution. Then, a clear answer shows the key idea has landed.

Download the 4th grade adding fractions worksheet answers as a PDF with the button below and keep it with your notes.

4th grade adding fractions worksheet answers: frequently asked questions

Do answers have to be written as mixed numbers?

Answers greater than 1 are usually written as mixed numbers in fourth grade, but improper fractions are also correct. For example, $\frac{11}{8}$ and $1\frac{3}{8}$ name the same amount. Also, follow your teacher’s directions, and when unsure, write both forms.

Why does the key regroup one whole as a fraction?

A whole can be written as a fraction with the same numerator and denominator, such as $\frac{6}{6}$. Borrowing one whole gives you six more sixths to work with. This is what makes $7\frac{2}{6} – 3\frac{5}{6}$ possible without a negative number. A quick check like this takes only a few seconds and prevents most errors.

What if my decomposition of 5/6 differs from the key?

Many answers are right in problem 6. Any two fractions with denominator 6 and numerators that add to 5 work, such as $\frac{1}{6} + \frac{4}{6}$ or $\frac{2}{6} + \frac{3}{6}$. Check by adding your two parts and confirming they make $\frac{5}{6}$.

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