The material attempts to find the maximum number of non-congruent figures that can be generated from a nine-pin geoboard, and considers the maximum number of figures possible on boards of any size. The exploration starts by grouping sets of pin patterns into groups of equivalent classes. (MP)

Illustrated is the use of isometric graph paper in the discovery of nonstandard area formulas. The use of definitions, geometric construction, record keeping, and conjectures about triangles, rhombuses, hexagons, parallelograms, isosceles trapezoids, rectangles, and trapezoids are described. (YP)

A new approach to classifying quadrilaterals is presented that tries to classify all possible combinations of shapes and angles by removing the traditional Euclidean viewpoints. The document concludes with a brief look at other types of polygons. (MP)

Possible ways of mechanization for counting using a binary system are discussed. Shows a binary representation of the numbers and geometric models having eight triples of lamps. Provides three problem sets. (YP)

Equations or systems of equations can be associated with letters of the alphabet printed in the coordinate plane. Messages can be coded and decoded with a computer or by hand. (SD)

Presents a variety of mathematics activities for students to solve. Sections are included on geometrical dissection, prime numbers, trigonometry, and number concepts. (RH)

The 1985 Indiana Mathematics Contest included tests in Algebra (First Course), Geometry, Algebra (Second Course), and Comprehensive. Test-writing responsibilities were delegated to mathematics and mathematics education faculties at four state universities, with the mathematical content based on course objectives in the state guidelines. Fourteen…

A method is given for the analysis of geodesic domes involving plane geometry. The method shows how to calculate all necessary angles and chords, given the length of one side. (MP)

This material shows how to use basic techniques, principles of counting, and geometry to count squares on geoboards. The methods are elementary in that the proofs are easily conceptualized. A discussion of other approaches illustrates that easily stated problems may lead to very difficult and sophisticated methods. (MP)

A possible logical flaw based on similar triangles is discussed with the Sherlock Holmes mystery, "The Muskgrave Ritual." The possible flaw has to do with the need for two trees to have equal growth rates over a 250-year period in order for the solution presented to work. (MP)

A complete characterization of minimum conditions for congruence of quadrilaterals is presented. Convex quadrilaterals are treated first, then concave quadrilaterals are considered. A study of such minimum conditions is seen to provide some interesting and important activities for students. Only background in triangle congruence is necessary. (MP)

This module, designed for use at the high school level as a four- to eight-hour topic, includes: the geometry of a sphere, the coordinate system used to describe points on the earth's surface, parallel and meridian sailing, and the solution of right spherical triangles. (Author/MK)

The second Indiana Mathematics Contest included tests in Algebra (First Course), Geometry, Algebra (Second Course), and Comprehensive. Test-writing responsibilities were delegated to mathematics and mathematics education faculties at four state universities, with the mathematical content based on course objectives in the state guidelines. Fourteen…

A series of maps is presented for coloring with the fewest possible colors. (SD)

This monthly column contains teaching suggestions on: using codes to convey information, flow proofs in geometry, and volleyball and probability. (MP)