Give three pairs of prime numbers whose difference is 2. [Remark: Two prime numbers whose difference is 2 are called twin primes].
Answer: Three pairs of prime numbers whose difference is 2 are (5, 7), (11, 13) and (17, 19). A pair of prime numbers whose difference is 2 are called twin primes. The alternative names given to twin primes are prime twin or prime pair.
