Question

Which of the following pairs are always co-primes?

(i) two prime numbers
(ii) one prime and one composite number
(iii) two composite numbers

Answer 1

(i) Two prime numbers are always co-primes to each other.
Example: 7 and 11 are co-primes to each other.

(ii) One prime and one composite number are not always co-prime.
Example: 3 and 21 are not co-primes to each other.

(iii) Two composite numbers are not always co-primes to each other.
Example: 4 and 6 are are not co-primes to each other.