Puzzle Details

The local CD shop operates an unusual discount policy. The discount on the next purchase is worked out on the current purchase in the following way: for every whole pound spent you get 0.5% discount on the next purchase. For example, if you purchased £8.99 on the first purchase, you would then get a 4% discount on the next purchase and so on. You can make as many purchases as necessary.

You need to buy 7 CDs, costing, £11.50, £12.00, £12.00, £12.50, £13.00, £13.00 and £14.50 - what is the cheapest method of buying them?

Answer: Purchase 1: £11.50, £12.00, £12.00, £12.50 = £48.00 (which gives a 24% discount on the next purchase). Purchase 2: £13.00, £13.00, £14.50 = £40.50 minus 24% discount = £30.78. For a total cost of £78.78.

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