In 1973, statistician Francis Anscombe published four small datasets sharing the same mean, the same spread and the same trend line. Yet once plotted, one forms a straight line, another a curve, another is skewed by a single outlier. In 2017, researchers pushed the idea further: same summary figures, but a scatter plot shaped like a dinosaur.
How many different structures can you build with six classic 2-by-4 Lego bricks of the same colour? The company used to quote just over 102 million. In 2005, Danish mathematician Søren Eilers recounted everything by computer: 915,103,765 combinations. The official estimate had been too low by a factor of about nine.
Fold an A4 sheet in half and you get an A5 with the same proportions. That only works for one ratio between length and width: about 1.414, the square root of 2. The A0 format measures exactly one square metre, and A4 is a sixteenth of it. With standard 80-gram-per-square-metre paper, an A4 sheet therefore weighs exactly 5 grams.