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April 23, 2014

April 23, 2014

Posted by **Sarah** on Sunday, May 17, 2009 at 9:32am.

I'm sitting my maths non-calculator GCSE tomorrow and am currently revising. I'm doing a practise paper and am currently stuck on this question:

Express A in terms of w.

3w + 20 A

-------- = --------

200 A + 12

-- Can you explain to me step by step how to solve this problem? I'm really bad with understanding maths lingo btw :)

Thank you!

- Maths -
**Sarah**, Sunday, May 17, 2009 at 9:33amArg, that problem is supposed to be

3w + 20

-------

200

is equal to

A

----

A + 12

- Maths -
**Reiny**, Sunday, May 17, 2009 at 9:40amwrite it like this, it is easier to read in this format.

(3w+20)/200 = A/(A+12)

cross-multiply to get

(3w+20)(A+12) = 200A

3Aw + 36w + 20A + 240 = 200A

3Aw - 180A = -240 - 36w

switch all the signs

180A - 3Aw = 240 + 36w

factor out an A

A(180 - 3w) = 240 + 36w

divide by 180 - 3w

A = (240+36w)/(180-3w)

A = (80+12w)/(60-w)

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