In addition to 10 and

A book without words.
To the left a small house and a small house on the right.
Each double page, we see the inside of one of the two houses, and a perforated separator page small windows hints inside the other house.
So we count the number of boyfriends on one side, and try to guess how many there are on the other side, knowing you can not see them all through the windows.
On each shot, a boyfriend moves from one house to another.
This book serves as well as to familiarize themselves with the supplements to 10 etc ...

But what is so fun is that it is also the subject of a great observation, indeed every step of the home elements also move.
My 3 year old daughter claims the lot. To give an idea, she knew count to 10, but do not guess the complement to 10. I think it's interesting when the child knows almost count.