A set of wooden number blocks and counting rods aid children in learning simple mathematics concepts from young age. The colourful number blocks and rods stimulate children’s senses of recognition.

1-2 year old : Teach him/her to learn to recognize and distinguish colors and do simple activities like colours sorting and matching of simple numbers
2-3 years old : You can teach them basic math operations like addition and subtraction. 
3 years old and above : You can teach the child division and multiplication. 

You can also use the rods as a spindle box activities ( Montessori Style) . Refer to this link for more information on how to use it:
http://www.infomontessori.com/mathematics/numbers-through-ten-spindle-boxes.htm