A hands-on introduction to the CATS-approach to mathematics, Count&Add in Time&Space, where mathematics is learned as a natural science investigating multiplicity, and using 1digit numbers only.

The following activities are included: A) Counting by bundling and stacking. Re-counting, B) Cup-writing using decimals, C) Decimal Recounting, D) Selling from a stock of two stacks, E) Adding stacks on top of a stack, F) Adding stacks next to a stack as integration, F) Handling overloads, G) Multiplying and dividing with the bundle-size, H) Solving equations, I) Discuss the advantages and disadvantages of cup-writing, decimal-counting and 1digit mathematics: Is 10 a cognitive bomb to be introduced as the last bundle-size?

Target audience: Pre-service and in-service teacher training for primary school and preschool.
Participants: Max 30.
Goal: To experience mathematics as a natural science investigating its roots, multiplicity.
Bring: A matchbox.