Give this mind-melting maths puzzle ago – and it'll require you to use your language skills too. Just 10% of people got it ...

This optical puzzle challenges the viewer to find the hidden number '99' among a pattern of repeating '67' numbers. It tests ...

Roula Khalaf, Editor of the FT, selects her favourite stories in this weekly newsletter.

Note: Most subscribers have some, but not all, of the puzzles that correspond to the following set of solutions for their local newspaper ... ARE TWO RULES IN LIFE: NUMBER ONE, NEVER QUIT!