Which of the given pairs form a co-prime numbers pair?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is Option 4 i.e. (11, 21).
Co-prime numbers:- Two numbers that have no other common factor than 1.
Since the other pairs have common factors other than 1 as:-
⇒ (21, 42) have 7 and 3 as other factors
⇒ (9, 63) have 3 and another 3 as prime factors
⇒ (36, 15) have 3, as common prime factors
But in (11, 21) there are no other common factors other than 1
Hence,
(11, 21) is the pair of co-prime numbers pair