Abstract: A spinner for randomly selecting a number has a very low friction bearing between a transparent spinner member and a transparent base plate. In one embodiment the base and spinner are formed of a transparent plastic such as Plexiglas, with a cone point set screw mounted in a threaded hole of the base plate and providing a narrow point for seating of the spinner member. A transparency with annularly arranged numbers may be placed at the bottom side of the transparent base plate, and different numerical arrays or symbol arrays may be selected. The spinner member has a central hole fitted with a central hub that has a recess formed into an internal cone shaped apex. The cone angle of the set screw point is steeper than that in the apex of the hub recess, so that the spinner member rests essentially only on the narrow point of the set screw.

Abstract: A set of polyhedrons have shapes capable of fitting together, in one or more ways, into a solid geometric shape such as a rectangular solid or more specifically, a cube. The polyhedrons include five-sided polyhedrons made up of a regular tetrahedron and an irregular tetrahedron abutted together as one solid; alternately, the two separate tetrahedra can be included in lieu of one or more of the five-sided polyhedrons, for assembly in the puzzle. The set of polyhedrons includes separate irregular tetrahedra and may include a regular octahedron. Preferably each shape of polyhedron is in a different color. In a preferred embodiment, the polyhedrons are all solid throughout and are of the same density, and that density is preferably the same density as water to enable the teaching of certain relationships. The set of polyhedrons function not only as a puzzle, for fitting into a transparent housing such as a cube, but also for educational purposes in teaching geometry.

Abstract: A portable, preferably pocket-sized electronic calculator includes provision for disabling the use of certain keys on its keyboard. By holding down a number key or certain of the function keys for a predetermined period of time such as two to four seconds, the user can disable the selected number or function. This allows the calculator to be used effectively in teaching factoring and various mathematical properties and leads the student to innovate in substituting different numbers and functions in solving problems in the student's own way. For discontinuing all key disabling a reset key preferably is provided.

Abstract: A device for assigning numbers to products having casings, such as electronic calculators, has at least two digit wheels, each preferably having digits 0 through 9. One of the digit wheels is transparent, while the other may be opaque, with a light background. The digits on each of the two wheels are offset from radial lines such that two-digit numbers can be made with selected digits juxtaposed. If three digit wheels are included the tens wheel has digits centered on radial lines. The casing of the product to be numbered has a number viewing window and an internal peg on which the digit wheels are held and can be rotated for adjustment, as well as at least one peg or pin for engaging registry holes to align and maintain the digit wheels in proper position. In a preferred embodiment the digit wheels are manipulated to the proper number by removing the back from the casing.

Abstract: An electronic timing device has a transparent liquid crystal display for use on an overhead projector, for projecting a large image of the LCD numerals on a screen or wall of a classroom, for timing of tests or other activities. The timer has a plastic casing, various function keys, a solar cell and/or battery, other internal electronics and a transparent liquid crystal display. Foldable legs of the timer, when open, maintain the timer a set distance above the light stage of the projector so as to prevent the LCD from overheating. One of the foldable legs, in the closed position, serves as protection and as a reflective backing for the LCD, so that the timer can function as a desk top LCD clock in the closed position. The timing device can function as a clock or timer in various modes.

Abstract: A hand-held calculator has a transparent window carrying a liquid crystal display as well as transparent number and function key locations such that when placed on an overhead projector, the calculator can be used to demonstrate to a classroom of students all operations performed in a sequence of mathematical operations. The plastic casing of the calculator has one or more small holes passing through the casing at corners, so that a string or line can be used to tether the calculator to the overhead projector, preventing damage to the calculator from a fall to the floor. A further feature of the calculator is a protrusion or foot at each corner of the back of the calculator casing, for holding the back surface of the calculator slightly above the light platform of the overhead projector, for cooling of the liquid crystal display by air passing between the light table and calculator.

Abstract: A hand-held calculator has a transparent window carrying a liquid crystal display as well as transparent number and function key locations such that when placed on an overhead projector, the calculator can be used to demonstrate to a classroom of students all operations performed in a sequence of mathematical operations. The plastic casing of the calculator has one or more small holes passing through the casing at corners. Another feature of the calculator is an improved keyboard of relatively small domain size for each key, with a spacer grid on the back surface of the keyboard membrane panel overlay element, effective to provide pressure isolation of an active key from adjacent keys and also to prevent other pressures on the keyboard from causing mistaken entries. A further feature of the calculator is a protrusion or foot at each corner of the back of the calculator casing.

Abstract: An item storage device with a plurality of open-topped storage pockets in a matrix of rows and columns is formed of a single sheet of material, preferably of woven fabric. The single sheet is lapped over in a series of horizontal fold lines, forming alternating three-ply areas and single-ply areas. An overlap opening at the top of each three-ply area or row forms the pockets of that row. Left and right ends of the folded sheet are folded on a vertical fold line to form a small hem which is stitched on a vertical line to form closed margins at left and right. Horizontal stitch lines are made to hold at least two of the three plies together along horizontal lines which define the bottoms of the pockets. Additional vertical stitch lines are made to define and separate the pockets laterally. In preferred embodiments a series of circular grommets are secured through a doubled-over fabric hem along the top edge of the carrying device, to enable suspending the device vertically.