A bargain ..... or not!

I don't have a cold but I always like to keep a couple of spare boxes of tissues in the cupboard.

I nipped into my local (smallish) supermarket to buy some Kleenex as I was down to my last box.  

First deal .... buy a double pack for £3 .... I was just about to add the pack to my basket when I noticed another offer right beside the first ... buy a triple pack for £5.

I managed, just, without resorting to pencil and paper that at the first price I could buy 5 x 2 packs for £15 and for the second 3 x 3 packs for £15 ..... surely 10 boxes is better value than 9!