It's easy when it's Bear Math
Recently we bought this great book in a yard sale, it's called Bears! Bears! Bears! by Scholastic. It comes with a handful of small cute plastic bears.
My 3-year old is fascinated by the bears (plays with them all the time) AND by the book, which teaches some early math concepts. For example, it tells to put equal amounts of bears into two balloons (see pic above). Or, set bears sitting facing each other - is one left over - so she can observe even/odd numbers. Or, you can measure by bears since each one is exactly one inch.
A great concept, unfortunately the book is not available much anywhere. Originally it was only distributed via school market. But, some folks sell it used at Amazon (probably the bears will not be included in these used versions, is my guess...).
Anyway, you know it but it's good to be reminded: when it's fun, learning is easy.