Fractions · Grades 4, 5
Mixed Numbers and Improper Fractions: Converting Both Ways
Quick answer
An improper fraction has a top number bigger than its bottom number, like seven quarters. A mixed number writes the same amount as a whole number plus a fraction, like one and three quarters. To go from improper to mixed, divide the top by the bottom: the quotient is the whole number and the remainder becomes the new top. To go back, multiply the whole number by the bottom and add the top.
What you'll learn
- Change an improper fraction into a mixed number
- Change a mixed number into an improper fraction
- Choose the form that suits the job in front of you
Two ways to write the same amount
Look at where sits.
The dot is past but not yet at . Counting from , four quarters got you to , and three more carried you along.
So the same spot has two names:
- is an improper fraction: the top number is bigger than the bottom.
- is a mixed number: a whole number next to a fraction.
The word improper is unfortunate. There is nothing wrong with .
Improper to mixed: divide
The bottom number tells you how many parts make one whole. So ask how many whole groups fit.
For , ask how many s fit into .
- The quotient is the number of wholes.
- The remainder is the parts left over.
- The bottom number never changes.
Mixed to improper: multiply, then add
Go the other way by asking how many parts there are in total.
For : each whole is thirds, and there are wholes, so that is thirds. Add the extra third.
Why the multiply-then-add rule works
It is not a trick. It is addition written out.
Rewrite the as thirds, since :
Now both parts are thirds, so they add directly:
The came from , and the was already there. That is exactly “multiply the whole by the bottom, then add the top”.
Which form should you use?
| Job | Better form |
|---|---|
| picturing an amount | mixed number |
| measuring with a cup or ruler | mixed number |
| multiplying or dividing | improper fraction |
| comparing two amounts | either, once the bottom numbers match |
Most calculations convert to improper form first, do the work, then convert back at the end. A mixed number is a sum in disguise, and sums are awkward to multiply.
Worked examples
Common mistakes
Practice problems
-
Write as a mixed number.
Hint
How many s fit into , and what is left?
Answer
Full solution
remainder , so the answer is .
-
Write as a mixed number.
Answer
Full solution
remainder , so the answer is .
-
Write as an improper fraction.
Answer
Full solution
, then . The answer is .
-
Write as an improper fraction.
Answer
Full solution
, then . The answer is .
-
Write as a mixed number or whole number.
Answer
Full solution
remainder , so there is no fraction part. The answer is the whole number .
-
Write as a mixed number in simplest form.
Hint
Convert first, then simplify the leftover fraction.
Answer
Full solution
remainder , giving .
Divide both parts of by to get , so the answer is .
-
Which is bigger, or ?
Hint
Put both in the same form first.
Answer
Full solution
, and is less than .
So is bigger.
-
A recipe calls for cups of flour. Your cup is marked in quarters. How would you say that amount out loud?
Answer
Two and a quarter cups.
Full solution
remainder , so .
Fill the cup twice, then once more to the quarter mark.
-
Nina writes , because she added and . What went wrong?
Hint
Is bigger or smaller than ?
Answer
She added the whole number to the top instead of multiplying first. The answer is .
Full solution
Each whole is , so three wholes are sevenths. Adding the extra gives .
Her answer is less than one whole, which cannot be right for a number that starts with a .
-
Write a mixed number and an improper fraction for the amount three eighths past .
Answer
, which is .
Full solution
The mixed number is .
Converting: , then , so the improper fraction is .
Frequently asked questions
What is an improper fraction?
It is a fraction whose top number is bigger than or equal to its bottom number, like seven quarters. Nothing is wrong with it. It names an amount of one whole or more.
How do I turn an improper fraction into a mixed number?
Divide the top number by the bottom number. The whole-number part of the answer goes in front, and the remainder becomes the new top number over the same bottom number.
How do I turn a mixed number into an improper fraction?
Multiply the whole number by the bottom number, then add the top number. That total goes over the same bottom number. Two and one third becomes seven thirds.
Which form should I use?
Mixed numbers are easier to picture and to measure with. Improper fractions are easier to multiply and divide with, so most calculations start by converting to improper form.
Key terms in this lesson
- Quotient
- The quotient is the answer to a division. In 12 ÷ 4 = 3, the 12 is the dividend, the 4 is the divisor, and the 3 is the quotient.
Standards alignment
This lesson covers the following Common Core State Standards for Mathematics.
- CCSS.MATH.CONTENT.4.NF.B.3Number and Operations—FractionsUnderstand a fraction a/b with a > 1 as a sum of fractions 1/b.
- CCSS.MATH.CONTENT.4.NF.B.3bNumber and Operations—FractionsDecompose a fraction into a sum of fractions with the same denominator in more than one way, recording each decomposition by an equation. Justify decompositions, e.g., by using a visual fraction model.
- CCSS.MATH.CONTENT.4.NF.B.3cNumber and Operations—FractionsAdd and subtract mixed numbers with like denominators, e.g., by replacing each mixed number with an equivalent fraction, and/or by using properties of operations and the relationship between addition and subtraction.