# Interpretation of math question help appreciated?

• Feb 20th 2011, 02:25 PM
David Green
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.

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
• Feb 20th 2011, 02:34 PM
emakarov
Under offer (2), you get 1.25 litres for £1.20, or £0.96 per litre.
• Feb 20th 2011, 02:55 PM
e^(i*pi)
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
• Feb 20th 2011, 03:04 PM
David Green
Thanks for that information, much appreciated

David
• Feb 21st 2011, 11:33 AM
David Green
Quote:

Originally Posted by e^(i*pi)
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
• Feb 21st 2011, 11:39 AM
e^(i*pi)
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

The cost per litre is $\dfrac{1.20}{1.25} = \dfrac{6}{5} \cdot \dfrac{4}{5} = \dfrac{24}{25} = 96p$
• Feb 21st 2011, 12:03 PM
David Green
Quote:

Originally Posted by e^(i*pi)
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

The cost per litre is $\dfrac{1.20}{1.25} = \dfrac{6}{5} \cdot \dfrac{4}{5} = \dfrac{24}{25} = 96p$