i say that its however many nuggets you can buy with all the money in the world. if u take all the money in circulation in the world, u can only buy as much nuggets as u have money for. if u cant afford it u cant buy it. who would want all those nuggets anyway......

Should the question read: "...the _smallest_ number...it is not possible to buy..."? kfennessy correctly points out the largest number it is not possible to buy.

There are only boxes with 6,9 and 20. So there are some quantities you can't buy. You can't get 1,2,3,4,5.....also can't buy 7 or 8. The largest impossible number is 43. From 44 upwards it is always possible with combinations of 6,9 and 20. Try it.