Question

Which of the following pairs of numbers is/are coprime ?

• A. $(2,4)$
• B. $(1,3)$
• C. $(3,6)$
• D. $(2,7)$

Answer 1

Answer: (B), (D)

The correct options are
B $(1,3)$
D $(2,7)$

$(2,4)\to$ set of two different even numbers can never be coprime as they have common factors $1$ and $2.$

$(1,3)\to$ yes they are coprime because every natural number is coprime with $1.$

$(3,6)\to$ not coprime because they have common factors $1$ and $3.$

$(2,7)\to$ yes they are coprime because they have only one common factor i.e. $1.$
Note: Set of two different prime numbers are always coprime to each other.