(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Calculate 7*11 + 9*11^-1 in the group Z20

2. Relevant equations

3. The attempt at a solution

77+ (9*1/11) in group Z20

77 + 9/11

17 +11x= 20mod+9

My solution was 12, this makes 149 on both sides when you multiply the mod times 7.

I am doing independent study and the computer program I am using says the answer is 16.

What am I doing wrong? Btw, what is the difference between ring congruence arithmetic and regular congruence arithmetic? They seem pretty similar.

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Problems with inverses in arithmetic in ring z

**Physics Forums | Science Articles, Homework Help, Discussion**