Solved: Prove that the set of positive rational numbers is
Chapter 4, Problem 56E(choose chapter or problem)
Prove that the set of positive rational numbers is countable by setting up a function that assigns to a rational number p/q with gcd(p, q) = 1 the base 11 number formed by the decimal representation of p followed by the base 11 digit A, which corresponds to the decimal number 10, followed by the decimal representation of q.
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