This video is about how to ‘rationalise the denominator’ – which is just a way of changing the bottom of a fraction to a whole number – and gives a few examples:
5 divided by 3√2 becomes 5√2 / 6
and
18 divided by √3 becomes 6√3
Like many of these exercises, in isolation, they appear to be fairly irrelevant – it’s only when you need to manipulate equations in higher levels, that they can be useful. Most ‘rationalise the denominator’ questions appear on non calculator GCSE maths papers (including Edexcel, AQA, OCR and Educas), and are approximately grade 6+. The questions are usually 2 – 4 marks.
Please do try some of the questions in the additional posts listed below – with a little practice learning how to rationalise the denominator can be fairly straightforward.
This series of 3 minute math is designed as a quick reminder for some of the main topics. I hope they help to provide a focus and a way forward. If you need any more detail please search the site or contact me – always pleased to answer any questions!
Here’s some additional posts, that might be of interest:
THANK YOU so much Mr Simon. Took me less than 3 minutes to understand what
my teacher took me 30minutes to teach me!
Thank you this was really helpful, but what do i do when it’s: 6+ root 8
root 2 ?
how can u solve.. 3 root 7 + 3 root 7??
If only all of the teachers would explain maths the way you do, sir! 🙂
Thank you for posting all of those helpful videos.
Please like and leave a comment!
Visit https://www.3minutemaths.co.uk for real maths, tips and techniques.
Will do – I’ll let you know when posted.
Would it be possible to do a video on Set Theory (Venn Diagrams), if so
that would be very useful!
Thanks and glad it helped 🙂
Very helpful, keep up the good work !!
Hi – try ‘3 Minute Math – Angles and Number of Sides in Regular Polygons 2’
or ‘3 Minute Math – Angles and Number of Sides in Regular Polygons.’ I hope
these help and all best S
Hi Will – you need to multiply top and bottom by root6. That will give you
3 root6 on the top and 6 on the bottom. If you then divide top and bottom
by 3 you get root6 / 2 Hope this helps and all best S
Hi ive been asked to rationalise the denominator of 3/root6… the answer
according to the mark scheme is root6/2. Could you tell me how to get to
that answer? Thanks
Will do and will let you know when posted. All the exterior angles of a
regular polygon add up to 360 degrees… the interiors can be calculated by
180 – exterior. Hope this helps and thanks for the request. All best S
Please can you do a video on finding interior and extirior angles in
regular and irregular polygons?