A mathematical challenge for you all.....

[AuntyQuated]

Problem of the day---

me and a friend were in M&S today she had 2 things in her basket - one for £12 and one for £15

in my basket were 4 things for £8, £10, £10, and £10.

to get the best deal from the "2 for 3 offer" my friend paid for 3 items of £15,£10 & £10. so she paid £25

i paid for 3 items of £12,£10 and £8. i paid £22

BIG QUESTION

how much do i owe her??? (we want to share the discount)

every time we work it out we come up with a different answer.
please someone..put us out of our misery>

Yes, Roisin, headache has outweighed bargain.
anyway maybe i needed a bit of a mental exercise!!!

hang on a minute

SHE only bought two items so in effect was not entitled to any discount so by you giving one of your things over you saved her some money.

I don't think you owe her anything do you?

(or am I being tight?)

take the total money saved £65-£47 = £18

and go to the pub

If you're sharing the discount equally I would say:

She should pay 12+15 = 27
You should pay 8+10+10+10 = 38

The proportionate discount (assuming they are all in 3for2) is the two lowest priced items = £18/2 = £9

Therefore: 27-9 = £18
38-9 = £29

You owe her: £7

I am being tight then?

oh well - thats probably why I'm filthy rich

But by taking 3 goods through teh checkout she enabled AQ to get teh discount therefore she should be recognised for that. I would have proportioned it.

Ok, fwiw (again), I like Twiglett's way the best.

But AQ would have got £8 discount anyway...she already had more than 3 items.

27 plus 38 = 65
38/65 = 58%
Discount = (22 + 25) - 65 = 18

AQ entitled to 58% of 18 = 10.44

but i thought they wanted to split the discount?

Think I'm agreeing with JJ's method

Was your friend's second item £12 or £10 - if she paid £25 I assume it was £10. Anyway, the discount you got on the 3 items you paid for is yours. For the 3 items paid by your friend, the full value was £37 but she paid £25 - if you apportion the saving against the individual full price of the items, you owe her 25/37 * 10, i.e. £7 (£6.76 to be precise).

Oops, if the full price was £25, the amount due her is 25/35 * 10, still £7 (well, £7.14).

Damn, I mean £35.

AQ- why didn't you just pay for your friends stuff and she could have given you £27?

The complication is that a lot of ways are right; it all depends on how you want to divide up the discount (ie what you think is fair).

I think you owe her £5.48. Probably the same method as JJ

I total, you paid £47 for £65 of goods so to ratio down your full price use 47/65.

Friends goods were £27 full price. 27 x 47/65 = £19.52. Friend actually paid £25 so you owe her £25 - £19.52 = £5.48

you've all got me tittering now!

LOL