Indira Vijaysimha

O n observing the triple (25, 125, 225) in which 125 is a perfect cube, 25 and 225 are perfect squares, and the three numbers are in arithmetic progression (AP), I felt that 125 is a very special perfect cube which is guarded by two perfect squares on either side at equal distance.

A surprising discovery we make is that 125 is guarded by two perfect squares in another way, namely: (81, 125, 169); here, 81 and 169 are perfect squares, and the three numbers are in AP as earlier.

The article talks about a simple activity which can be performed with students of primary, middle and high school. The shape that is used to discuss here is a square and hence it is expected that students know the basic properties of a square. The article also talks about using lines. Even if students don't have a Euclidean notion of definition of a line, that idea can be instilled as the teacher executes this activity.

This article describes an activity where students created different geometrical shapes using a closed-loop string and developed conceptual understanding by engaging with properties of the shapes. The activity encouraged them to think deeply about the meaning of points, straight lines, edges, faces, and angles of geometrical shapes. Using standard models which are generally available, students only get to view geometrical shapes or build them by following a set of instructions.

Beginning with this issue, we start the TearOut series. In this article, we focus on investigations with dot sheets. Pages 1 and 2 are a worksheet for students, pages 3 and 4 give guidelines for the facilitator

An article on Harmonic Triangular Triples

These are excellent GeoGebra exercises for students helping them to develop and practise skills of visualisation, logical sequencing, making connections and recalling theory. Read on.

The concept of digital root of a natural number has been known for some time. Before the development of computer devices, the idea was used by accountants to check their results. We will examine the basis for this procedure presently.
An octagon is constructed within a square by joining each vertex of the square to the midpoints of the two sides remote from that vertex. Eight line segments are thus drawn within the square, creating an octagon (shown shaded). The following two questions had been posed: (i) Is the octagon regular? (ii) What is the ratio of the area of the octagon to that of the square?

In this issue’s task we work with right-angled triangles, isosceles as well as scalene. The activity has enormous scope for creativity, visualisation, investigation, pattern recognition, documentation and conjecture. Facilitators should encourage students to come up with proofs for conjectures that they make.


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