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Math Help - Interpretation of math question help appreciated?

  1. #1
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    Interpretation of math question help appreciated?

    I have a question, which seems badly worded to me?

    Question;

    A super market has the following two offers on fruit smoothies

    1/ 25% off the usual price
    2/ 25% extra free

    The usual price of the smoothie is 1.20 per litre carton.

    The question asks;

    Calculate the price per litre of smoothie under offer (2)

    Surely if the offer 2 is 25% extra free, then the price is still the same at 1.20?

    or is it 1.51, which then suggests that its not free?

    Any help appreciated
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  2. #2
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    Under offer (2), you get 1.25 litres for 1.20, or 0.96 per litre.
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  3. #3
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    The price will be the same in real life but here the question asks the price per litre. In other words you'll need to work out the new volume, then divide the price (which is the same) by the new volume

    Evidently your new volume is simple 1L + 0.25L = 1.25L while your price remains 1.20

    Thus the price per litre is 96p


    (Interestingly it turns out that offer 1 gives you 90p per litre thus making it the better offer)

    edit: because I'm bored the equilibrium point (when the two offers are equal in price per litre is 18.03%) - this falls well outside the scope of your question as does everything in red
    Last edited by e^(i*pi); February 20th 2011 at 04:09 PM.
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  4. #4
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    Thanks for that information, much appreciated

    David
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  5. #5
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    Quote Originally Posted by e^(i*pi) View Post
    The price will be the same in real life but here the question asks the price per litre. In other words you'll need to work out the new volume, then divide the price (which is the same) by the new volume

    Evidently your new volume is simple 1L + 0.25L = 1.25L while your price remains 1.20

    Thus the price per litre is 96p


    (Interestingly it turns out that offer 1 gives you 90p per litre thus making it the better offer)

    edit: because I'm bored the equilibrium point (when the two offers are equal in price per litre is 18.03%) - this falls well outside the scope of your question as does everything in red
    I understand what you have said above I think, but am a little confused were 0.96 p came from?

    I see it as; 1000 / 1025 = 0.97 p, but this can't quite be right because 0.97 x 1.25 = 1.21?

    Having looked on the calculator, the integar after 7 is a 5, so surely it can't be rounded down?

    David

    Edited to say, sorry late learning curve. I see where the 0.96p arrived from now?

    1.20 / 1.25L = 0.96 p
    Last edited by David Green; February 21st 2011 at 12:36 PM. Reason: late learning curve
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  6. #6
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    Where did 1025 come from? The price per litre is given by the price (unchanged) by the new volume

    Your new volume is 1L + 25%. 25% of 1L is 0.250L so your new volume is 1.25L

    Your new price is the same as your old price: 1.20

    The cost per litre is \dfrac{1.20}{1.25} = \dfrac{6}{5} \cdot \dfrac{4}{5} = \dfrac{24}{25} = 96p
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  7. #7
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    Quote Originally Posted by e^(i*pi) View Post
    Where did 1025 come from? The price per litre is given by the price (unchanged) by the new volume

    Your new volume is 1L + 25%. 25% of 1L is 0.250L so your new volume is 1.25L

    Your new price is the same as your old price: 1.20

    The cost per litre is \dfrac{1.20}{1.25} = \dfrac{6}{5} \cdot \dfrac{4}{5} = \dfrac{24}{25} = 96p
    I did it my way lol

    1000 ml x 25% / 100 = 250 ml

    then I added the 1000 ml back to the 250 ml to get 1250 ml, then I divided 1250 by 1000 = 1.25 L

    Thanks for your help, my maths is not brilliant
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