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# What is the formula for working out the circumference of a circle?

By Lee Mansfield on the 11th of June, 2012

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By Filsan on the 8th of October, 2012

## Simplify expressions with surds into the form a + b3

Be warned this topic is Chuck Norris hard. Make sure you've done the related topics below before you try and get your head round this one...

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So if you put a square root sign around a number that is not a square number, then what you have written is a surd.

e.g. √10 is a surd, because 10 is not a square number. √9 is not a surd, because 9 is a square number, so you can write √9= 3

Even if the number under the square root sign is not a square number, it can still be simplified.

Write the starting number as a product of two new numbers, where one of them is a square number (e.g. 45 -> 9 x 5).  Take the root of the square number, and write it outside of the root sign

e.g. √45 = √(9×5)=3√5

## Follow the links below to see how this topic has appeared in past exam papers

AQA Unit 2 March 2011 (H) - Page 11, Question 17

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