Mixed Numbers & Improper Fractions (SQA National 5 Maths): Revision Note

Exam code: X847 75

Roger B

Written by: Roger B

Reviewed by: Dan Finlay

Updated on

Converting between mixed numbers & improper fractions

What are mixed numbers & improper fractions?

  • A mixed number has an integer part and a fraction part

    • 3 3 over 4 has the whole number 3 and the fraction 3 over 4, meaning “three and three quarters”

  • An improper fraction is also known as a top-heavy fraction

  • An improper fraction is a fraction where the numerator is bigger than the denominator

    • 15 over 4 means “fifteen quarters”

  • Any fraction that is greater than 1 can be written as either a mixed number or an equivalent improper fraction

How do I convert a mixed number into an improper fraction?

  • Multiply the integer part by the denominator of the fraction part

    • For example, convert 4 6 over 7 into a top heavy fraction

    • 4 cross times 7 equals 28

  • Add the result to the numerator of the fraction part

    • 28 plus 6 equals 34

  • Write the 'new' numerator over the same denominator and ignore the integer part

    • 4 6 over 7 equals 34 over 7

  • You can also think of this as

4 6 over 7 equals 4 plus 6 over 7 equals 28 over 7 plus 6 over 7 equals fraction numerator 28 plus 6 over denominator 7 end fraction equals 34 over 7

How do I convert an improper fraction into a mixed number?

  • Divide the numerator by the denominator

    • For example, to convert 22 over 3 into a mixed number 

    • 22 divided by 3 equals 7 remainder 1

  • The integer part of the mixed number is the whole number

  • The fraction part is the remainder over the denominator

    • 22 over 3 equals 7 1 third

  • You can also think of this as

22 over 3 equals fraction numerator 21 plus 1 over denominator 3 end fraction equals 21 over 3 plus 1 third equals 7 plus 1 third equals 7 1 third

Examiner Tips and Tricks

An exam question is unlikely to ask you specifically to change a mixed number into an improper fraction or vice versa.

However this is often an essential step in Paper 1 questions on adding, subtracting, multiplying or dividing fractions.

Worked Example

(a)     Write 5 3 over 4 as an improper fraction.

(b)     Write 17 over 5 as a mixed number.

Answer:

Part (a)

Multiply the whole number by the denominator, and add to the numerator

Keep the denominator the same

fraction numerator open parentheses 5 cross times 4 close parentheses plus 3 over denominator 4 end fraction

Simplify

23 over 4

Part (b)

Divide the top by the bottom

17 ÷ 5 = 3 remainder 2

The final answer is 3, with 2 parts still left over

Leave the 3 as the whole number part and put the 2 over the original denominator of 5

3 2 over 5

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Roger B

Author: Roger B

Expertise: Maths Content Creator

Roger's teaching experience stretches all the way back to 1992, and in that time he has taught students at all levels between Year 7 and university undergraduate. Having conducted and published postgraduate research into the mathematical theory behind quantum computing, he is more than confident in dealing with mathematics at any level the exam boards might throw at you.

Dan Finlay

Reviewer: Dan Finlay

Expertise: Maths Subject Lead

Dan graduated from the University of Oxford with a First class degree in mathematics. As well as teaching maths for over 8 years, Dan has marked a range of exams for Edexcel, tutored students and taught A Level Accounting. Dan has a keen interest in statistics and probability and their real-life applications.