3 yrs. & up. Children can play with them like ordinary blocks, and thus are engaged instead of threatened. Children stack the blocks next to other objects imitating Greek and Egyptian methods of measurement, and achieve a tactile understanding of the metric system. Arithmetic principles are firmly established by hands on work and observation. A valuable tool for children from 3 to 14 years old. Conforms to N.C.T.M. standards for cognitive and skills development.