Abstract: A combination of devices that demonstrate visually and on an intuitive level mathematical principles relating to the circle including the number &pgr;, the relationship between circumference, diameter, radius and &pgr;, and the relationship between the area of a circle formed of circle sectors and an approximate parallelogram obtained by rearranging the circle sectors.

Abstract: A concrete manipulative for teaching the properties of odd and even numbers. The manipulative includes an elongated channel having end walls at each end, and a plurality of rods that fit at least partially within the channel. The rods are in two sets of different lengths, with each length being represented by more than one rod. Rods of even length are visually and/or tactilely distinguishable as a set from rods of odd length. The elongated channel displays markings at precise intervals, with the spacing between markings generally being twice the length of the shortest rod. Through a variety of activities involving placement and manipulation of various combinations of the rods within the channel, students are able to identify properties of odd and even numbers.

Abstract: A concrete manipulative for teaching the properties of odd and even numbers. The manipulative includes an elongated channel having end walls at each end, and a plurality of rods that fit at least partially within the channel. The rods are in two sets of different lengths, with each length being represented by more than one rod. Rods of even length are visually and/or tactilely distinguishable as a set from rods of odd length. The elongated channel displays markings at precise intervals, with the spacing between markings generally being twice the length of the shortest rod. Through a variety of activities involving placement and manipulation of various combinations of the rods within the channel, students are able to identify properties of odd and even numbers.