"which I measured with my rulers"

Then sell them at school for a dollar and make $58 bucks =)

Or you could just be a decent person and donate them

probably just wanted to do that because she was hoping that he would change his mind

That wouldn't be clever from her - more rulers = more money.

Depends on the inventory system. A lot of store's systems don't allow you to just say "oh theres 5 of those" and scan one since they each have a specific spot in the system. You have to scan each so that it can remove each item from the inventory.