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How do you subtract mixed numbers from Year 6?

Published in Fraction Subtraction 3 mins read

In Year 6, you subtract mixed numbers by generally subtracting the whole number parts and then subtracting the fractional parts. Here's a breakdown of the methods you might learn:

Methods for Subtracting Mixed Numbers

Here are a few methods taught in Year 6 for subtracting mixed numbers:

1. Subtracting Whole Numbers and Fractions Separately

  • Step 1: Subtract the Whole Numbers. Take away the whole number part of the second mixed number from the whole number part of the first mixed number.

  • Step 2: Subtract the Fractions. Subtract the fractional part of the second mixed number from the fractional part of the first mixed number. Make sure the fractions have a common denominator before subtracting.

  • Step 3: Combine the Results. Combine the result from Step 1 (the difference of the whole numbers) with the result from Step 2 (the difference of the fractions).

Example:

Calculate 5 2/3 - 2 1/3

  1. Subtract the Whole Numbers: 5 - 2 = 3
  2. Subtract the Fractions: 2/3 - 1/3 = 1/3
  3. Combine the Results: 3 + 1/3 = 3 1/3

2. Converting to Improper Fractions

  • Step 1: Convert to Improper Fractions. Convert each mixed number to an improper fraction. To do this, multiply the whole number by the denominator of the fraction, add the numerator, and then put the result over the original denominator.

  • Step 2: Find a Common Denominator. If the improper fractions do not have the same denominator, find a common denominator.

  • Step 3: Subtract the Fractions. Subtract the numerators of the improper fractions. Keep the common denominator.

  • Step 4: Simplify (if needed). If the resulting improper fraction is top-heavy (the numerator is larger than the denominator), convert it back to a mixed number. Simplify the fraction if possible.

Example:

Calculate 4 1/2 - 1 1/4

  1. Convert to Improper Fractions:
    • 4 1/2 = (4 * 2 + 1) / 2 = 9/2
    • 1 1/4 = (1 * 4 + 1) / 4 = 5/4
  2. Find a Common Denominator: The common denominator for 2 and 4 is 4. Convert 9/2 to 18/4.
  3. Subtract the Fractions: 18/4 - 5/4 = 13/4
  4. Simplify: 13/4 = 3 1/4

Tips and Considerations

  • Borrowing: If the fraction you are subtracting is larger than the fraction you are subtracting from (when using the first method), you will need to "borrow" 1 from the whole number, convert it to a fraction with the same denominator, and add it to the first fraction.
  • Simplifying: Always simplify your final answer if possible.

By using these methods, Year 6 students can effectively subtract mixed numbers.

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