Question

Which of the following is a pair of coprime?

• A. $5,15$
• B. $2,20$
• C. $15,16$
• D. $3,12$

Answer 1

The correct option is C

$15,16$

Explaination for the correct option:

Any two successive integers/numbers are co-primes.

or

We can say that those consecutive numbers which have the only common factor $1$ are called co-primes.

So, $15,16$ are successive integers/numbers and they have only $1$as common factor that's why they are co-prime numbers.

Explaination for the incorrect option:

1. $5,15$ are not consecutive integers. So, they are not co-primes.
2. $2,20$ are not consecutive integers, So, they are not co-primes.
3. $3,20$ are not consecutive integers, So, they are not co-primes.

Conclustion statement:

So, option C is the correct option.