A brain teaser that has gone viral online challenges people to count the number of triangles in it. There are more than 20 triangles. Can you count them all?

In fact, only one out of five individuals can accurately count all of the hidden triangles. So if you believe you're among the top 20 per cent most observant folks, you'll need to demonstrate it.

Triangle Counting and Analysis in Large Graphs Publication Trend The graph below shows the total number of publications each year in Triangle Counting and Analysis in Large Graphs.