Here is a neat way of using maths to pretend to memorise a pack of cards. Amaze your friends! Astound your family!

Count around the clock.

There are many errors that can occur when numbers are written, printed or transferred in any manner. Luckily, there are schemes in place to detect, and in some cases even correct, such errors almost immediately. Emily Dixon takes a break and discovers that codes are not just for sleuths.