A directory of useful objects found on the web for teaching Maths.

Using algebra to describe patterns mathematically. This activity employs various visual patterns, constructed with matchsticks. Drag the matches around to study each pattern and work out its underlying mathematical nature. See if you can describe each pattern using algebra.see details …

It is easy to forget that "summary statistics" such as mean, range, deviation, correlation etc are only summaries. Anscombe's Quartet is an informative demonstration of the dangers of overlooking this fact. This activity uses 3 sets of values from the quartet, as well as supports student experimentation using their own data. Calculation of sum, mean, standard devation and plotting of points is included.see details …

This applet lets you explore the domain and range of various functions.see details …

Four clearly different and visually distinct datasets produce the same summary statistics.
Check out the Datasaurus Dozen. While different in appearance, each dataset has the same summary statistics (mean, standard deviation, and Pearson's correlation) to two decimal places.
via Flowing Datasee details …

Dr James Maynard explains the Twin Prime Conjecture, it's history and recent progress.see details …

Using only a pair of compasses, ruler and pencil, here's how to construct an egg shape from arcs of circles.see details …

Fatih Erikli uses a simulation that works like a disaster spread model applied to social networks to give an idea of how disinformation spreads.see details …

In this series of videos, Grant Sanderson (3Blue1Brown) want you to feel that you could have invented calculus for yourself.
In this first video, we see how unraveling the nuances of a simple geometry question can lead to integrals, derivatives, and the fundamental theorem of calculus.
More:
Chapter 2 - The paradox of derivative
Chapter 3 - Derivative formulas through geometry
Chapter 4 - Visualizing the chain rule and product rule
Chapter 5 - Derivatives of exponentials
Chapter 6 - Implicit differentiation, what's going on here?
Chapter 7 - Limits
Chapter 8 - Integration and the fundamental theorem of calculus
Chapter 9 - What does area have to do with slope?
Footnote - Higher order derivatives
Chapter 10 - Taylor series
Alternative link takes you to the YouTube playlist for this series.see details …

An example of a heat map representing real-world data. Each cell shows the percentage of crashes at that time involving the selected factor. This is for US data.see details …

This is not just a multiplication grid, but an actual representation of the products.see details …

Ben sparks demonstrates how seemingly random numbers can create amazing patterns.
Click through to the video for GeoGebra files.see details …

A comprehensive reference on the Golden Ratio by Dr Ron Knott, University of Surrey.see details …

Deane investigates making boxes out of squares of paper and considers which will give the maximum volume.see details …