Asked by Sarah

Hey :)

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



<i>-- What does the question mean?

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


Thank you!
Answered by Sarah
Arg, that problem is supposed to be

3w + 20
-------
200


is equal to

A
----
A + 12

Answered by Reiny
write 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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