Mixed numbers (Edexcel GCSE Maths): Revision Notes
Mixed numbers
What are mixed numbers and improper fractions?
Mixed numbers are numbers that contain both a whole number and a fraction combined together. They show complete units plus a leftover fractional part.
For example: represents 3 whole units plus of another unit.
Improper fractions are fractions where the top number (numerator) is bigger than the bottom number (denominator). This means the fraction represents more than one whole unit.
Examples of improper fractions include: , , and . Notice how in each case, the numerator (top number) is larger than the denominator (bottom number).
Converting between mixed numbers and improper fractions
Understanding how to change between these two forms is essential for mathematical calculations. Both forms represent the same value, but different operations require different forms.
Converting mixed numbers to improper fractions
To change a mixed number into an improper fraction, follow these steps:
- Multiply the whole number by the denominator
- Add the result to the numerator
- Keep the same denominator
Worked Example: Converting Mixed Number to Improper Fraction
Convert to an improper fraction
Step 1: Multiply the whole number by the denominator
Step 2: Add the result to the numerator
Step 3: Keep the same denominator Therefore:
Converting improper fractions to mixed numbers
To change an improper fraction into a mixed number:
- Divide the numerator by the denominator
- The whole number becomes your answer
- Any remainder becomes the new numerator
- Keep the same denominator
Worked Example: Converting Improper Fraction to Mixed Number
Convert to a mixed number
Step 1: Divide the numerator by the denominator remainder
Step 2: The quotient becomes the whole number part:
Step 3: The remainder becomes the new numerator:
Step 4: Keep the same denominator:
Therefore:
The golden rule for calculations
The Golden Rule: You must always convert mixed numbers to improper fractions before doing any mathematical operations like multiplication or division.
This rule prevents errors and makes calculations much simpler to complete accurately.
Working with mixed numbers in calculations
When performing calculations with mixed numbers, always remember to convert first, then calculate, then convert back if needed.
Multiplication example
Worked Example: Multiplying Mixed Numbers
Calculate
Step 1: Convert to improper fraction
Step 2: Multiply the fractions
Step 3: Convert back to mixed number remainder Therefore:
Subtraction example
Worked Example: Subtracting Mixed Numbers
Calculate
Step 1: Convert both to improper fractions
Step 2: Find common denominator and subtract
Step 3: Convert back to mixed number
Exam tips and common mistakes
When working with mixed numbers in exam questions, these strategies will help you succeed:
- Always convert mixed numbers to improper fractions before calculating
- Check your work by thinking about whether your answer makes sense
- In word problems, consider if the result should be more or less than the original amounts
- Show your working clearly - you can earn marks even if your final answer isn't perfect
- Remember you cannot use a calculator for these questions, so practice mental arithmetic
Word problem tip: If someone is sharing items, each person should get less than the total amount. Use this logic to check if your answer is reasonable.
Key Points to Remember:
- Mixed numbers combine whole numbers and fractions (like )
- Improper fractions have numerators larger than denominators (like )
- Always convert mixed numbers to improper fractions before calculating
- To convert mixed to improper: multiply, add, keep the denominator
- To convert improper to mixed: divide and use the remainder as the new numerator