Sets are intuitive - you have a basket and you put stuff in it. But what about the empty basket? How do you write it? And why is that important how you write it? Here's a hands on example of the empty sets in your kitchen.
We know that if you start counting at one object the number of thing is the same as if you start with something different - but kids don't. Here are some thoughts on counting that can put you in a different mindset when dealing with children and counting.