What time is it in the Rieman sphere????????

MODULO 7

To add 3 and 5 modulo 7, you start at 0, count 3 clockwise, and then a further 5 clockwise, this time ending on 1. To multiply 3 by 5 modulo 7, you start at 0 and count 3 clockwise 5 times, again ending up at 1. We would write 

3 + 5 ≡ 1 mod 7 and 3 × 5 ≡ 1 mod 7.

As we mentioned above, there is nothing special about 7. We can put any number of “hours” around our clock face and do arithmetic modulo any whole number. Our usual clocks can be used to do arithmetic modulo 12. If you go to a 2-hour movie starting at 11 o’clock, you will get out at 1 o’clock. This illustrates the following equality in arithmetic modulo 12:

11 + 2 ≡ 1 mod 12.