This is a case study involving a preschool teacher who produced and tested a design called “Combined Activity,” which uses a combination of hands-on mathematics manipulatives and computer software to help preschoolers understand number concepts. The purpose of the action research was to describe how the children experienced the Combined Activity in learning number concepts by using a combination of hands-on manipulatives and computer software. The participants were a preschool teacher and 20 threeto five-year-old preschoolers who spent three weeks using the Combined Activity at a preschool in an urban area in Florida, U. S. A. Results of this study show that the participants in the Combined Activity were able to interact with the teacher and peers using diverse communication skills in much more varied mathematical learning environments than by lecture alone. The findings imply that a teacher needs to design the physical setting taking into consideration the culturally and developmentally appropriate learning environment (Copple & Bredkamp, 2009; Gestwicki, 2009; Tobin, 2011) through on-going observation. The teacher also needs developmentally appropriate materials, reflective activity plans, and clear guidelines as well as attention to the children’s linguistic and cultural backgrounds.