For a start: how many small tetrahedra, like the blue model shown, were used to make the 6.5 metre high red balloon model shown below.
The smallest tetrahedron (Stage 0), the blue model, is made from 6 balloons, each […]
Image starting with an equilateral triangle and replacing each edge by a zig-zag curve made up of 4 pieces. Each of the 4 pieces is one third of the length of the line segment it replaces so it looks as if equilateral triangles have been attached to the shape. Now imagine repeating […]
This workshop guide provides learning activities that explore the ways in which arithmetic and geometric series are used in simple and compound interest calculations related to loans (including pay-day loans) , investments, annuities, hire-purchase, inflation etc. and there is an explanation of how APR is calculated. Ideas are given for practical ways […]
Multiply out these expressions:
What do you notice?
Does this pattern continue?
Can you prove it?
What does this tell you about the sum to n terms of the geometric series with first term 1 and common ratio r?
Why do we get a formula for all values of r except r = 1?
The squares in the diagram are to help us visualise an infinite geometric sum and we are not summing the areas of the squares, simply the lengths along the x-axis. The squares have side lengths given by powers of r: where 0 < r < 1 .