MA05-04 Maths Watch
Rationalising the denominator (Higher)
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In this lesson
In this video you'll learn about rationalising the denominator (higher) for GCSE Maths, with worked examples and the mistakes examiners report. By the end you'll be able to rationalise a surd denominator by multiplying both the numerator and the denominator by the same root, rather than simply deleting the root sign from the denominator.
What it covers
- 1:08 Rationalising the denominator (higher): why + the engine
- 3:50 Run it properly, on the question from the opening
- 6:42 One more wrinkle and you have the full method: a number sitting in front of the root on the bottom
- 8:18 Before the exam corner, one full question with everything in it
- 12:09 What's next
Key words
For: AQA GCSE 8300, Edexcel GCSE 1MA1, Eduqas GCSE C300, Cambridge IGCSE 0580, Edexcel IGCSE 4MA1, OCR GCSE J560
On the specification
| Board | Spec | Statement |
|---|---|---|
| AQA GCSE 8300 | N8 | Calculate exactly with fractions |
| Edexcel GCSE 1MA1 | N8 | Calculate exactly with fractions and multiples of π |
| Eduqas GCSE C300 | HN8 | Calculate exactly with fractions, surds and multiples of π; simplify surd expressions involving squares (e.g. √12 = √(4 × 3) = √4 × √3 = 2√3) and rationalise denominators |
| Cambridge IGCSE 0580 | E1.18 | Understand and use surds, including simplifying expressions. |
| Edexcel IGCSE 4MA1 | H1.4A | Understand the meaning of surds |
| Edexcel IGCSE 4MA1 | H1.4B | Manipulate surds, including rationalising a denominator |
| OCR GCSE J560 | 3.03a | Use fractions in exact calculations without a calculator. |
| OCR GCSE J560 | 3.03b | Simplify expressions with surds, including rationalising denominators. |
For teachers
This GCSE Maths lesson teaches rationalising the denominator (Higher). By the end, students should be able to rationalise a surd denominator by multiplying both the numerator and the denominator by the same root, rather than simply deleting the root sign from the denominator. It works through three worked examples and the mistakes examiners report.