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Year 10 - Maths

Rationalising a two term denominator

Surds

Unit Summary

In this unit pupils will learn how to recognise surds, handle them in calculations and rationalise fractions with surds as denominators.

Lesson Summary

You will learn to use the technique of rationalising the denominator to transform a fraction to an equivalent fraction.

Key Notes

  • Fractions should be given in their simplest term.
  • The denominator should be written as simply as possible.
  • Combining your knowledge of equivalent fractions and the distributive law will help.

Vocabulary To Learn

  • Surd: A surd is an irrational number expressed as the root of a rational number.

Common Mistakes To Avoid

  • Pupils may struggle to see why using the difference of two squares is important.

3 Quick Questions (With Answers)

1. Solve this in steps: explain the method from this lesson and why each step matters.

Fractions should be given in their simplest term. The denominator should be written as simply as possible.

2. Use this key word in a maths sentence and explain it clearly. 'Surd'

A surd is an irrational number expressed as the root of a rational number. Use this word when showing your method, then check your final answer is reasonable.

3. Spot and fix this common maths mistake.

Mistake: Pupils may struggle to see why using the difference of two squares is important. Correction: The grid method for multiplication can be used to explore why two of the terms cancel each other.

More Lessons In This Unit

Browse all guides in the Year 10 Maths guide library.