Changing the subject of a formula - grade 6 GCSE

This video is all about changing the subject of a formula and forms part of the playlist by the same name. I've also added to the playlist on GCSE higher revision.

This question is around grade 6 GCSE and involves cross multiplication as well as factorisation:

(r+s) / 8s = (r-s) / 8n

Make r the subject.


I hope the video helps and please do leave a comment - thanks!

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[justfunandgames]

Unfortunately I haven’t had time to thank you so I apologise I’ve been extremely busy with my A levels. However Simon I seriously cannot thank you enough for helping me through my GCSE’s (I got a 7 (A) in my results) just gone in August. I now am studying A level maths. I often watched your videos for tutorials and I seriously cannot express how talented you are at teaching mathematics, I wish you all the best! Thank you!

[danielmitchell]

Amazing, literally the only good explanation there is out there

[simonlevett]

Simon, are some formulae impossible to solve for a particular letter ? In this example is it possible to make s the Subject ? I get to the point when I'm trying to factorise by placing s outside the brackets, but I cannot get rid of the s squared. Any help would be appreciated.

[darkspice]

So very helpful. I cant thank you enough ❤

[aygamer]

Shouldn't you further simplify the fraction by factorising 8 out of the numerator and denominater, then both 8s will cancel?

[carlaalleng]

Simone you're a big help but could you please write a little bigger.