There are so many creative designed clocks available in the markets but this clock is really unique, it only uses 9s and some mathematic symbols to display the time.

In fact, if the formulas are not arranged and located in the normal positions and sequences, I bet you can’t tell the time immediately; even if you are so good in mathematic, you need to take few seconds to tell the time.

Don’t believe? Copy down all the twelve formulas on a paper and try to solve them one by one, then you will know.