Math riddles and puzzles come in plenty of different varieties. Some more straightforward number puzzles require calculations ...

Thankfully, the puzzles appear to remain the same ... There are only two possible digits that could fit here. Feel free to ...

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

Plus, you can let us know what you think of the puzzles by emailing at [email protected]. We look forward to hearing from you.