need not be identical, that should read.
Maths questions are fine, really -- it's wording them in English that's the problem! And, of course, why the answers have to be so implausible. Far better to, I guess... not distribute all of the items? If she kept a few for herself then you could do, say, 30 bags with 7 stickers each, 5 milk trays, and 12 quality streets, and then the rest could be for small goodies for answering questions one lesson.