Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

We know that there is a one-to-one correspondence between the $r$ with $0\le r\lt20$ with $gcd(r,20)=1$ and the pairs $(r_1,r_2)$ where $0\le r_1\lt4$, where $0\le r_2\lt5$ such that $gcd(r_1,4)=1$ and such that $gcd(r_2,5)=1$. Exhibit this correspondence.

share|improve this question
    
A lot like your other question. –  mick Oct 12 '12 at 14:01

1 Answer 1

Perhaps you should read about the Chinese Remainder Theorem. You may also find it helpful to take some specific pairs (r,s) (of integers modulo 4 and 5, respectively) and "assemble" them to form a residue class modulo 20.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.