9/30/2012 -- Junior Circle: Clock arithmetic (Oleg Gleizer)
We will visit the planet Heptadium in a galaxy far, far away. The planet makes one full spin around its axis in 7 heptahours, so the folks inhabiting the planet divide the dials of their clocks into 7 parts. A heptahour is divided further into 49 heptaminutes, a heptaminute has 49 heptaseconds. We will study the Heptadium way of timekeeping and the related mod 7 and mod 49 arithmetics.