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    • Thread Starter

    Basically ive got an assignment which is maths and i dont understand anything on it .. its due in really soon and if i dont pass this im going to fail my year. If it's ok ill use this save creating threads.. just hope someone can help me (its got 5) main questions with subs of them.

    This is one of them

    phone contract is fixed monthly at 9.99 (includes VAT) after that its 2.2pence rated at 20%. in the question X represents number of minuites over 100 and Y the resulting cost of the bill .

    Express the relationship between X and Y as a linear expression ?
    • Thread Starter


    Hey Sam,

    We've got exactly the same problem here at Shrewsbury doing the Staffs Business Course

    The only linear expression i could come up with is Y=a+bX.

    I'd put that in pencil for now, but i'm working on it. I've done most of the other questions but that one is a right folker.

    Craig James.

    In fact, i'm pretty sure i've got the answer!

    for 2 b)

    x = 20, y = 10.43
    x = 50, y = 11.09 (0.022 x 50) + (9.99)
    y = 20, x = 455
    y = 30, x = 909.5

    The large x values in the second half seem to make sense to me, since its only 2.2p a minute, so it would take a long time to accumulate an additional £10 or £20 on the phone bill at such a low rate.

    As for part g, you essentially want to "undo" the old VAT and then multiply it by the new one.

    Suppose there is some number A which is the base rate before 20% VAT is added. Then 1.20*A = 9.99 - from this you can work out A. You can then use 1.175*A = your new rate at the slightly lower VAT. You should get an answer close to the original £9.99, but slightly less

    I've got some other answers as well if you want to go over them mate!
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Updated: April 13, 2011
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